Monolithic heater bodies

ABSTRACT

A monolithic heater body may include a combustor body, a hot-side heat exchanger body, and an eductor body. The combustor body may define a combustion chamber and a conditioning conduit circumferentially surrounding the combustion chamber. The conditioning conduit may fluidly communicate with the combustion chamber at a distal portion of the combustion chamber. The hot-side heat exchanger body may define a hot-side heat exchanger that includes a heating fluid pathway fluidly communicating with a proximal portion of the combustion chamber. The eductor body may define an eduction pathway fluidly communicating with a downstream portion of the heating fluid pathway and a proximal portion of the conditioning conduit.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to each of the following U.S.Provisional Applications, the contents of which are incorporated hereinby reference in their entirety for all purposes as if set forthverbatim: App. No. 62/850,599, filed May 21, 2019; App. No. 62/850,623,filed May 21, 2019; App. No. 62/850,678, filed May 21, 2019; App. No.62/850,692, filed May 21, 2019; and App. No. 62/850,701, filed May 21,2019. The present application also incorporates by referenceInternational Patent Application Number PCT/US2020/033674 filed on May20, 2020 in its entirety for all purposes.

FIELD

The present subject matter relates generally to energy conversionsystems, power generation systems, and energy distribution systems. Thepresent subject matter additionally relates to heat exchangers and heatexchanger systems. The present subject matter further relates to pistonengine assemblies, such as closed-cycle engine systems. The presentsubject matter still further relates to systems and methods for controlor operation of one or more systems of the present subject matterherein.

BACKGROUND

Power generation and distribution systems are challenged to provideimproved power generation efficiency and/or lowered emissions.Furthermore, power generation and distribution systems are challenged toprovide improved power output with lower transmission losses. Certainpower generation and distribution systems are further challenged toimprove sizing, portability, or power density generally while improvingpower generation efficiency, power output, and emissions.

Certain engine system arrangements, such as closed cycle engines, mayoffer some improved efficiency over other engine system arrangements.However, closed cycle engine arrangements, such as Stirling engines, arechallenged to provide relatively larger power output or power density,or improved efficiency, relative to other engine arrangements. Closedcycle engines may suffer due to inefficient combustion, inefficient heatexchangers, inefficient mass transfer, heat losses to the environment,non-ideal behavior of the working fluid(s), imperfect seals, friction,pumping losses, and/or other inefficiencies and imperfections. As such,there is a need for improved closed cycle engines and systemarrangements that may provide improved power output, improved powerdensity, or further improved efficiency. Additionally, there is a needfor an improved closed cycle engine that may be provided to improvepower generation and power distribution systems.

Additionally, or alternatively, there is a general need for improvedheat transfer devices, such as for heat engines, or as may be applied topower generation systems, distribution systems, propulsion systems,vehicle systems, or industrial or residential facilities.

Furthermore, there is a need for improved control system and methods foroperating power generation systems as may include subsystems thatcollectively may provide improved power generation efficiency or reducedemissions.

BRIEF DESCRIPTION

Aspects and advantages will be set forth in part in the followingdescription, or may be apparent from the description, or may be learnedthrough practicing the presently disclosed subject matter.

In one aspect, the present disclosure embraces monolithic heater bodies,such as for use in connection with a closed-cycle engine. An exemplarymonolithic heater body may include a combustor body, a hot-side heatexchanger body, and an eductor body. The combustor body may define acombustion chamber and a conditioning conduit circumferentiallysurrounding the combustion chamber. The conditioning conduit may fluidlycommunicate with the combustion chamber at a distal portion of thecombustion chamber. The hot-side heat exchanger body may define ahot-side heat exchanger that includes a heating fluid pathway fluidlycommunicating with a proximal portion of the combustion chamber. Theeductor body may define an eduction pathway fluidly communicating with adownstream portion of the heating fluid pathway and a proximal portionof the conditioning conduit.

These and other features, aspects and advantages will become betterunderstood with reference to the following description and appendedclaims. The accompanying drawings, which are incorporated in andconstitute a part of this specification, illustrate exemplaryembodiments and, together with the description, serve to explain certainprinciples of the presently disclosed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure including the best mode, directed to oneof ordinary skill in the art, is set forth in the specification, whichmakes reference to the appended figures, in which:

FIG. 4.1.1 schematically depicts a cross-sectional view of an exemplaryclosed-cycle engine, which may be a regenerative heat engine and/or aStirling engine;

FIGS. 4.1.2A and 4.1.2B schematically depict an exemplary heater bodies,which, for example, may be included in the closed-cycle engine shown inFIG. 4.1.1;

FIGS. 4.1.3A, 4.1.3B, and 4.1.3C schematically depict a cross-sectionalperspective view of an exemplary heater body, which, for example, may beincluded in the closed-cycle engine shown in FIG. 4.1.1;

FIG. 4.1.4 schematically depicts a top view of an exemplary heater body,which, for example, may be included in the closed-cycle engine shown inFIG. 4.1.1;

FIG. 4.1.5 shows a flowchart depicting an exemplary method of heating aclosed-cycle engine, such as a regenerative heat engine;

FIGS. 4.1.6A and 4.1.6B schematically depict exemplary monolithicbodies, which may include monolithic body portions and/or monolithicbody-segments;

FIG. 4.1.7 schematically depicts another exemplary monolithic heaterbody;

FIGS. 4.1.8A-4.1.8G schematically depict exemplary heat shields that maybe included in a monolithic heater body and/or a monolithicbody-segment;

FIG. 4.1.9 schematically depicts a cross-sectional view of a portion ofan exemplary heater body, illustrating portions of an exemplary pistonbody and an exemplary heat-capture pathway;

FIG. 4.1.10 schematically depicts a cross-sectional view of an exemplaryan interface between a heater body and an engine body;

FIG. 4.2.1A shows a cross-sectional perspective view of an exemplarycombustor body portion of a heater body that may be included in theheater body shown in FIG. 4.1.3B;

FIG. 4.2.1B shows a cross-sectional perspective view of anotherexemplary combustor body portion of a heater body that may be includedin the heater body shown in FIG. 4.1.3B;

FIG. 4.2.2A schematically depicts a cross-sectional view of anperspective exemplary heater body that includes multi-stage combustion;

FIG. 4.2.2B schematically depicts a cross-sectional top-view of anexemplary combustion zone occupying a radially-inward portion of ahot-side heat exchanger;

FIG. 4.2.3A schematically depicts a cross-sectional view of an exemplarycombustor body that includes a venturi;

FIGS. 4.2.3B and 4.2.3C illustrate exemplary fluid velocity profiles forthe combustor body shown in FIG. 4.2.3A;

FIGS. 4.2.4A-4.2.4E schematically depict exemplary combustor vanes;

FIG. 4.2.5A shows a flowchart depicting an exemplary method ofcombusting a fuel;

FIG. 4.2.5B shows a flowchart depicting another exemplary method ofcombusting a fuel;

FIG. 4.3.1 schematically depicts a cross sectional view of an exemplaryfuel injector assembly according to an aspect of the present disclosure;

FIG. 4.3.8 schematically depicts a cross sectional view of an exemplaryfuel injector assembly according to an aspect of the present disclosure;

FIG. 4.4.1A shows a top cross-sectional view of an exemplary heatexchanger body portion of a heater body, such as the heater body shownin FIG. 4.1.3A;

FIG. 4.4.1B shows a top cross-sectional view of the exemplary heatexchanger body of FIG. 4.4.1A, with a plurality of heat transfer regionsindicated;

FIG. 4.4.2A shows a top cross-sectional view of an exemplary heatexchanger body portion of a heater body, such as the heater body shownin FIG. 4.1.3B;

FIG. 4.4.2B shows a top cross-sectional view of the exemplary heatexchanger body of FIG. 4.4.2A, with a plurality of heat transfer regionsindicated;

FIGS. 4.4.3A and 4.4.3B show top cross-sectional views of additionalexemplary embodiments of a heat exchanger body;

FIG. 4.4.4 shows a flowchart depicting an exemplary method of heating aplurality of heat transfer regions;

FIG. 4.5.2 schematically depicts a cross-sectional view of anotherexemplary working-fluid body that may be included in a heater body, suchas the heater body shown in FIG. 4.1.3B;

FIG. 4.5.3 schematically depicts a bottom cross-sectional view of anexemplary working-fluid body;

FIGS. 4.5.5A-4.5.5D schematically depict further aspects of an exemplaryheater body;

FIG. 4.5.6 shows a flowchart depicting an exemplary method of heating anengine-working fluid;

FIG. 5.1.28 provides an example computing system in accordance with anexample embodiment of the present disclosure.

Repeat use of reference characters in the present specification anddrawings is intended to represent the same or analogous features orelements of the present disclosure.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the disclosure,one or more examples of which are illustrated in the drawings. Eachexample is provided by way of explanation of the disclosure and notlimitation. In fact, it will be apparent to those skilled in the artthat various modifications and variations can be made in the presentdisclosure without departing from the scope of the disclosure. Forinstance, features illustrated or described as part of one embodimentcan be used with another embodiment to yield a still further embodiment.In another instance, ranges, ratios, or limits associated herein may bealtered to provide further embodiments, and all such embodiments arewithin the scope of the present disclosure. Unless otherwise specified,in various embodiments in which a unit is provided relative to a ratio,range, or limit, units may be altered, and/or subsequently, ranges,ratios, or limits associated thereto are within the scope of the presentdisclosure. Thus, it is intended that the present disclosure covers suchmodifications and variations as come within the scope of the appendedclaims and their equivalents.

It is understood that terms “upstream” and “downstream” refer to therelative direction with respect to fluid flow in a fluid pathway. Forexample, “upstream” refers to the direction from which the fluid flows,and “downstream” refers to the direction to which the fluid flows. It isalso understood that terms such as “top”, “bottom”, “outward”, “inward”,and the like are words of convenience and are not to be construed aslimiting terms. As used herein, the terms “first”, “second”, and “third”may be used interchangeably to distinguish one component from anotherand are not intended to signify location or importance of the individualcomponents. The terms “a” and “an” do not denote a limitation ofquantity, but rather denote the presence of at least one of thereferenced item.

Approximating language, as used herein throughout the specification andclaims, may be applied to modify any quantitative representation thatcould permissibly vary without resulting in a change in the basicfunction to which it is related. Accordingly, a value modified by a termor terms, such as “about,” “substantially,” and “approximately,” are notto be limited to the precise value specified. In at least someinstances, the approximating language may correspond to the precision ofan instrument for measuring the value, or the precision of the methodsor machines for constructing or manufacturing the components and/orsystems. For example, the approximating language may refer to beingwithin a 10 percent margin.

Here and throughout the specification and claims, range limitations arecombined and interchanged, such ranges are identified and include allthe sub-ranges contained therein unless context or language indicatesotherwise. For example, all ranges disclosed herein are inclusive of theendpoints, and the endpoints are independently combinable with eachother.

The heat transfer relationships described herein may include thermalcommunication by conduction and/or convection. A heat transferrelationship may include a thermally conductive relationship thatprovides heat transfer through conduction (e.g., heat diffusion) betweensolid bodies and/or between a solid body and a fluid. Additionally, orin the alternative, a heat transfer relationship may include a thermallyconvective relationship that provides heat transfer through convection(e.g., heat transfer by bulk fluid flow) between a fluid and a solidbody. It will be appreciated that convection generally includes acombination of a conduction (e.g., heat diffusion) and advection (e.g.,heat transfer by bulk fluid flow). As used herein, reference to athermally conductive relationship may include conduction and/orconvection; whereas reference to a thermally convective relationshipincludes at least some convection.

A thermally conductive relationship may include thermal communication byconduction between a first solid body and a second solid body, between afirst fluid and a first solid body, between the first solid body and asecond fluid, and/or between the second solid body and a second fluid.For example, such conduction may provide heat transfer from a firstfluid to a first solid body and/or from the first solid body to a secondfluid. Additionally, or in the alternative, such conduction may provideheat transfer from a first fluid to a first solid body and/or through afirst solid body (e.g., from one surface to another) and/or from thefirst solid body to a second solid body and/or through a second solidbody (e.g., from one surface to another) and/or from the second solidbody to a second fluid.

A thermally convective relationship may include thermal communication byconvection (e.g., heat transfer by bulk fluid flow) between a firstfluid and a first solid body, between the first solid body and a secondfluid, and/or between a second solid body and a second fluid. Forexample, such convection may provide heat transfer from a first fluid toa first solid body and/or from the first solid body to a second fluid.Additionally, or in the alternative, such convection may provide heattransfer from a second solid body to a second fluid.

It will be appreciated that the terms “clockwise” and“counter-clockwise” are terms of convenience and are not to be limiting.Generally, the terms “clock-wise” and “counter-clockwise” have theirordinary meaning, and unless otherwise indicated refer to a directionwith reference to a top-down or upright view. Clockwise andcounter-clockwise elements may be interchanged without departing fromthe scope of the present disclosure.

As used herein, the terms “additively manufactured” or “additivemanufacturing techniques or processes” refer generally to manufacturingprocesses wherein successive layers of material(s) are provided on eachother to “build-up,” layer-by-layer, a three-dimensional component. Thesuccessive layers generally fuse together to form a monolithic componentwhich may have a variety of integral sub-components.

Although additive manufacturing technology is described herein asproviding fabrication of complex objects by building objectspoint-by-point, layer-by-layer, typically in a vertical direction, othermethods of fabrication are possible and are within the scope of thepresent subject matter. For example, although the discussion hereinrefers to the addition of material to form successive layers, oneskilled in the art will appreciate that the methods and structuresdisclosed herein may be practiced with any additive manufacturingtechnique or manufacturing technology. For example, embodiments of thepresent disclosure may use layer-additive processes, layer-subtractiveprocesses, or hybrid processes. As another example, embodiments of thepresent disclosure may include selectively depositing a binder materialto chemically bind portions of the layers of powder together to form agreen body article. After curing, the green body article may bepre-sintered to form a brown body article having substantially all ofthe binder removed, and fully sintered to form a consolidated article.

Suitable additive manufacturing techniques in accordance with thepresent disclosure include, for example, Fused Deposition Modeling(FDM), Selective Laser Sintering (SLS), 3D printing such as by inkjetsand laserjets, Sterolithography (SLA), Direct Laser Sintering (DLS),Direct Selective Laser Sintering (DSLS), Electron Beam Sintering (EBS),Electron Beam Melting (EBM), Laser Engineered Net Shaping (LENS), LaserNet Shape Manufacturing (LNSM), Direct Metal Deposition (DMD), DigitalLight Processing (DLP), Direct Laser Melting (DLM), Direct SelectiveLaser Melting (DSLM), Selective Laser Melting (SLM), Direct Metal LaserMelting (DMLM), Binder Jetting (BJ), and other known processes.

The additive manufacturing processes described herein may be used forforming components using any suitable material. For example, thematerial may be plastic, metal, concrete, ceramic, polymer, epoxy,photopolymer resin, or any other suitable material that may be in solid,liquid, powder, sheet material, wire, or any other suitable form orcombinations thereof. More specifically, according to exemplaryembodiments of the present subject matter, the additively manufacturedcomponents described herein may be formed in part, in whole, or in somecombination of materials including but not limited to pure metals,nickel alloys, chrome alloys, titanium, titanium alloys, magnesium,magnesium alloys, aluminum, aluminum alloys, and nickel or cobalt basedsuperalloys (e.g., those available under the name Inconel® availablefrom Special Metals Corporation). These materials are examples ofmaterials suitable for use in the additive manufacturing processesdescribed herein, and may be generally referred to as “additivematerials.”

In addition, one skilled in the art will appreciate that a variety ofmaterials and methods for bonding those materials may be used and arecontemplated as within the scope of the present disclosure. As usedherein, references to “fusing” or “binding” may refer to any suitableprocess for creating a bonded layer of any of the above materials. Forexample, if an object is made from polymer, fusing may refer to creatinga thermoset bond between polymer materials. If the object is epoxy, thebond may be formed by a crosslinking process. If the material isceramic, the bond may be formed by a sintering process. If the materialis powdered metal, the bond may be formed by a melting or sinteringprocess, or additionally with a binder process. One skilled in the artwill appreciate that other methods of fusing materials to make acomponent by additive manufacturing are possible, and the presentlydisclosed subject matter may be practiced with those methods.

In addition, the additive manufacturing process disclosed herein allowsa single component to be formed from multiple materials. Thus, thecomponents described herein may be formed from any suitable mixtures ofthe above materials. For example, a component may include multiplelayers, segments, or parts that are formed using different materials,processes, and/or on different additive manufacturing machines. In thismanner, components may be constructed which have different materials andmaterial properties for meeting the demands of any particularapplication. In addition, although the components described herein areconstructed entirely by additive manufacturing processes, it should beappreciated that in alternate embodiments, all or a portion of thesecomponents may be formed via casting, machining, and/or any othersuitable manufacturing process. Indeed, any suitable combination ofmaterials and manufacturing methods may be used to form thesecomponents.

An exemplary additive manufacturing process will now be described.Additive manufacturing processes fabricate components usingthree-dimensional (3D) information, for example a three-dimensionalcomputer model, of the component. Accordingly, a three-dimensionaldesign model of the component may be defined prior to manufacturing. Inthis regard, a model or prototype of the component may be scanned todetermine the three-dimensional information of the component. As anotherexample, a model of the component may be constructed using a suitablecomputer aided design (CAD) program to define the three-dimensionaldesign model of the component.

The design model may include 3D numeric coordinates of the entireconfiguration of the component including both external and internalsurfaces of the component. For example, the design model may define thebody, the surface, and/or internal passageways such as openings, supportstructures, etc. In one exemplary embodiment, the three-dimensionaldesign model is converted into a plurality of slices or segments, e.g.,along a central (e.g., vertical) axis of the component or any othersuitable axis. Each slice may define a thin cross section of thecomponent for a predetermined height of the slice. The plurality ofsuccessive cross-sectional slices together form the 3D component. Thecomponent is then “built-up” slice-by-slice, or layer-by-layer, untilfinished.

In this manner, the components described herein may be fabricated usingthe additive process, or more specifically each layer is successivelyformed, e.g., by fusing or polymerizing a plastic using laser energy orheat or by sintering or melting metal powder. For example, a particulartype of additive manufacturing process may use an energy beam, forexample, an electron beam or electromagnetic radiation such as a laserbeam, to sinter or melt a powder material. Any suitable laser and laserparameters may be used, including considerations with respect to power,laser beam spot size, and scanning velocity. The build material may beformed by any suitable powder or material selected for enhancedstrength, durability, and useful life, particularly at hightemperatures.

Each successive layer may be, for example, between about 10 μm and 200μm, although the thickness may be selected based on any number ofparameters and may be any suitable size according to alternativeembodiments. Therefore, utilizing the additive formation methodsdescribed above, the components described herein may have cross sectionsas thin as one thickness of an associated powder layer, e.g., 10 μm,utilized during the additive formation process.

In addition, utilizing an additive process, the surface finish andfeatures of the components may vary as need depending on theapplication. For example, the surface finish may be adjusted (e.g., madesmoother or rougher) by selecting appropriate laser scan parameters(e.g., laser power, scan speed, laser focal spot size, etc.) during theadditive process, especially in the periphery of a cross-sectional layerwhich corresponds to the part surface. For example, a rougher finish maybe achieved by increasing laser scan speed or decreasing the size of themelt pool formed, and a smoother finish may be achieved by decreasinglaser scan speed or increasing the size of the melt pool formed. Thescanning pattern and/or laser power can also be changed to change thesurface finish in a selected area.

After fabrication of the component is complete, various post-processingprocedures may be applied to the component. For example, post processingprocedures may include removal of excess powder by, for example, blowingor vacuuming. Other post processing procedures may include a stressrelief process. Additionally, thermal, mechanical, and/or chemical postprocessing procedures can be used to finish the part to achieve adesired strength, surface finish, a decreased porosity decreasing and/oran increased density (e.g., via hot isostatic pressing), and othercomponent properties or features.

It should be appreciated that one skilled in the art may add or modifyfeatures shown and described herein to facilitate manufacture of thesystem A10 provided herein without undue experimentation. For example,build features, such as trusses, grids, build surfaces, or othersupporting features, or material or fluid ingress or egress ports, maybe added or modified from the present geometries to facilitatemanufacture of embodiments of the system A10 based at least on a desiredmanufacturing process or a desired particular additive manufacturingprocess.

Notably, in exemplary embodiments, several features of the componentsdescribed herein were previously not possible due to manufacturingrestraints. However, the present inventors have advantageously utilizedcurrent advances in additive manufacturing techniques to developexemplary embodiments of such components generally in accordance withthe present disclosure. While certain embodiments of the presentdisclosure may not be limited to the use of additive manufacturing toform these components generally, additive manufacturing does provide avariety of manufacturing advantages, including ease of manufacturing,reduced cost, greater accuracy, etc.

In this regard, utilizing additive manufacturing methods, evenmulti-part components may be formed as a single piece of continuousmetal, and may thus include fewer sub-components and/or joints comparedto prior designs. The integral formation of these multi-part componentsthrough additive manufacturing may advantageously improve the overallassembly process, reduce potential leakage, reduce thermodynamic losses,improve thermal energy transfer, or provide higher power densities. Forexample, the integral formation reduces the number of separate partsthat must be assembled, thus reducing associated time, overall assemblycosts, reduces potential leakage pathways, or reduces potentialthermodynamic losses. Additionally, existing issues with, for example,leakage, may advantageously be reduced. Still further, joint qualitybetween separate parts may be addressed or obviated by the processesdescribed herein, such as to desirably reduce leakage, assembly, andimprove overall performance.

Also, the additive manufacturing methods described above provide muchmore complex and intricate shapes and contours of the componentsdescribed herein to be formed with a very high level of precision. Forexample, such components may include thin additively manufacturedlayers, cross sectional features, and component contours. As anotherexample, additive manufacturing may provide heat exchanger surfaceareas, volumes, passages, conduits, or other features that may desirablyimprove heat exchanger efficiency or performance, or overall engine orsystem performance. In addition, the additive manufacturing processprovides the manufacture of a single component having differentmaterials such that different portions of the component may exhibitdifferent performance characteristics. The successive, additive steps ofthe manufacturing process provide the construction of these novelfeatures. As a result, the components described herein may exhibitimproved functionality and reliability.

An exemplary engine c002 is shown in FIG. 4.1.1. The engine c002 may bea closed cycle engine, such as a regenerative heat engine and/or aStirling engine; however other engines including other closed-cycleengines and/or regenerative heat engines are also contemplated and thescope of the present disclosure embraces any engine. A closed-cycleengine c002 may include a heater body c100 and an engine body c050. Inthe embodiment shown, a closed-cycle engine c002 may include an enginebody c050 and a heater body c100 disposed on opposite sides of theengine body c050. For example, a first heater body c100 may be disposedat a first side of an engine body c050 and a second heater body c100 maybe disposed at a second side of an engine body c050. In still otherembodiments, a plurality of engine bodies c050 may be provided and/or asingle heater body c100 or a multitude of heater bodies c100 may beprovided. The closed-cycle engine c002 may include a piston assemblyc090 and a load device c092 operably inserted within an engine body c050and/or a heater body c100.

The closed-cycle engine c002 may be provided in the form of an engineassembly that includes one or more monolithic bodies or monolithicbody-segments as described herein. A monolithic body and/or a monolithicbody-segment may be fabricated using an additive manufacturingtechnology and may be void of any seams, joints, or the likecharacteristic of separately fabricated components. By way of example,an exemplary closed-cycle engine c002 may be assembled from an engineassembly that includes a first heater body c100 and a first engine bodyc050. The first heater body may define a first portion of a firstmonolithic body or a first monolithic body-segment, and the first enginebody may define a second portion of the first monolithic body or asecond monolithic body-segment operably coupled or operably couplable tothe first heater body.

Now turning to e.g., FIGS. 4.1.2A and 4.1.2B, 4.1.3A through 4.1.3C, and4.1.4, exemplary heater bodies c100 will be described. The presentlydisclosed heater bodies c100 may be used to supply heat to aclosed-cycle engine c002 such as a regenerative heat engine and/or aStirling engine. However, it will be appreciated that the presentlydisclosed heater bodies c100 may be used as a heating source in a numberof other settings, all of which are within the scope of the presentdisclosure. In some embodiments, at least a portion of the heater bodyc100 may define at least a portion of a closed-cycle engine c002, suchas a monolithic body or a monolithic body-segment of such a closed-cycleengine c002. For example, the monolithic body may be an additivelymanufactured monolithic body, or the monolithic body-segment may be anadditively manufactured monolithic body-segment. However, in addition oras an alternative to additive manufacturing technology, it will beappreciated that the monolithic body or various monolithic body-segmentsof a closed-cycle engine c002 may be formed using any desiredtechnology, all of which are within the scope of the present disclosure.

As shown, an exemplary heater body c100 may include a combustion chamberc102 and a recirculation pathway c104 configured to recirculatecombustion gas through the combustion chamber c102. The recirculationpathway c104 may include a hot-side heat exchanger c106 configured totransfer heat from circulating combustion gas to a heat input source,such as a working-fluid body c108 defining a heat transfer region havinga thermally conductive relationship with at least a portion of thehot-side heat exchanger c106. For example, heat from the combustion gasmay be transferred to the heat transfer region via an engine-workingfluid disposed within a working-fluid pathway c110. The working-fluidpathway c110 may be defined at least in part by the hot-side heatexchanger c106 and/or at least in part by the working-fluid body c108.The hot-side heat exchanger c106 may define a portion of therecirculation pathway c104. The heat transfer region may define a regionhaving a have a thermally conductive relationship with the heating fluidpathway.

The heat transfer region defined by the working-fluid body c108 mayinclude a solid body and/or a fluid pathway defined at least in part bythe solid body. In an exemplary embodiment, the hot-side heat exchangerc106 may include a plurality of heating fluid pathways that have a heattransfer relationship with a plurality of heat transfer regions. Forexample, the plurality of heat transfer regions have a thermallyconductive relationship with a corresponding portion of the plurality ofheating fluid pathways. Additionally, or in the alternative, the heattransfer regions may have a thermally convective relationship with aheating fluid flowing through the heating fluid pathways. The heattransfer regions may be circumferentially spaced about the longitudinalaxis of the heater body c100. Respective ones of the plurality of heattransfer regions may include a solid body and/or a fluid pathway definedat least in part by the solid body.

The working-fluid body c108 may include one or more portions of aclosed-cycle engine c002, such as a piston chamber c112 (e.g., a hotpiston chamber) and/or a regenerator body c114. A fluid pathway definedthe working-fluid body c108 may fluidly communicate with the pistonchamber and the regenerator body c114. The engine-working fluid disposedwithin the working-fluid pathway c110 may be an engine-working fluid,such as an inert gas, which may flow in an alternating fashion betweenthe piston chamber c112 and the regenerator body c114. The hot-side heatexchanger c106 may be provided in the form of a heat exchanger body. Theheat exchanger body may define a monolithic body portion of the heaterbody c100 or a monolithic body-segment operably coupled or operablycouplable to a monolithic heater body c100 or to one or more othermonolithic body-segments that make up the heater body c100.

The recirculation pathway c104 may additionally include a recirculationeductor c116 configured to utilize intake air flowing through an intakeair pathway c118 to entrain and/or accelerate combustion gas and therebyprovide a mixture of intake air and recirculating combustion gas to thecombustion chamber c102. The recirculation eductor c116 may also includean exhaust pathway c120 configured to discharge a portion of thecombustion gas as exhaust gas. The recirculation eductor c116 mayfluidly communicate with a downstream portion of the hot-side heatexchanger c106. The recirculation eductor c116 may be provided in theform of an eductor body. The eductor body may define a monolithic bodyportion of the heater body c100 or a monolithic body-segment operablycoupled or operably couplable to a monolithic heater body c100 or to oneor more other monolithic body-segments that make up the heater bodyc100.

In some embodiments, the heater body c100 may include a conditioningconduit c122 fluidly communicating with a downstream portion of therecirculation eductor c116 and an upstream portion of the combustionchamber c102. The conditioning conduct c122 may be configured to guidecombustion gas (e.g., a mixture of intake air and recirculatingcombustion gas) to the combustion chamber c102, and may be configuredwith a size and shape so as to condition one or more fluid dynamicproperties of the combustion gas flowing to the combustion chamber c122.Exemplary fluid dynamics properties that may be conditioned by theconditioning conduit c122 include pressure, pressure gradient, flowvelocity, velocity gradient, turbulence, vorticity, curl, and so forth.The conditioning conduit c122 may define a conduit volume selected toprovide one or more desired fluid dynamics properties of combustion gasflowing therethrough, and/or to allow for mixing of intake air withrecirculating combustion gas. In some embodiments, the conditioningconduit c122 may be configured to swirl combustion gas flowingtherethrough. For example, the conditioning conduit c122 may establishor sustain a vortex, which may enhance combustion quality in thecombustion chamber c102. Additionally, or in the alternative, combustiongas circulating through the conditioning conduit c122 may cool thecombustion chamber c102, with heat from the combustion chamber c102heating the combustion gas prior to entering the combustion chamberc102.

The combustion chamber c102 and the conditioning conduit c104 may beprovided in the form of a combustor body. The combustor body may definea monolithic body portion of the heater body c100 or a monolithicbody-segment operably coupled or operably couplable to a monolithicheater body c100 or to one or more other monolithic body-segments thatmake up the heater body c100.

The heater body c100 may additionally include a heat recuperator c124configured to utilize exhaust gas flowing through the exhaust pathwayc120 to preheat intake air flowing through the intake air pathway c118,thereby recuperating heat from the exhaust gas. The terms preheater andrecuperator may be used interchangeably; however, in some instances, theterm preheater may be used with reference to preheating intake airflowing through the intake air pathway c118, and the term recuperatormay be used with reference to recuperating heat from exhaust gas flowingthrough the exhaust pathway c120. The heat recuperator c124 may beprovided in the form of a heat recuperator body. The heat recuperatorbody may define a monolithic body portion of the heater body c100 or amonolithic body-segment operably coupled or operably couplable to amonolithic heater body c100 or to one or more other monolithicbody-segments that make up the heater body c100. As shown in FIG.4.1.2A, the heat recuperator c124 may be located downstream from therecirculation eductor c116 relative to the exhaust gas pathway c120 andupstream from the recirculation eductor c116 relative to the intake airpathway c118. The heat recuperator located as shown in FIG. 4.1.2A mayexchange heat between exhaust gas flowing through the exhaust gaspathway c120 and intake air flowing through the intake air pathway c118.In another embodiment, as shown in FIG. 4.1.2B, the heat recuperatorc124 may define a portion of the recirculation pathway c104. Forexample, the heat recuperator c124 may be located upstream from therecirculation eductor c116 relative to the recirculation pathway c120,while also being located upstream from the recirculation eductor c116relative to the intake air pathway c118. The heat recuperator located asshown in FIG. 4.1.2B may exchange heat between exhaust gas flowingthrough the exhaust gas pathway c120 and intake air flowing through theintake air pathway c118, and/or between combustion gas flowing throughthe recirculating pathway c104 and intake air flowing through the intakeair pathway c118.

One or more fuel nozzles c126 may be operably coupled to the heater bodyc100. Fuel may be supplied to the combustion chamber c102 by one or morefuel lines c103. For example, the one or more fuel nozzles c126 may beoperably coupled to the combustion chamber c102. Fuel injected into thecombustion chamber c102 may combine with circulating combustion gas toprovide a suitable air-to-fuel ratio. The fuel and at least a portion ofthe circulating combustion gas may be combusted in the combustionchamber so as to generate hot combustion gas. The combustion chamberc102 may fluidly communicate with an upstream portion of the hot-sideheat exchanger c106, thereby suppling the hot combustion gas to thehot-side heat exchanger c106 for heating the working-fluid body c108.One or more intake air pathways c118, one or more exhaust gas pathwaysc120, one or more recirculation pathways c104, and one or more fuellines c103 may collectively define a primary flowpath c121.

FIGS. 4.1.3A, 4.1.3B, and 4.1.3C schematically depict cross-sectionalperspective views of an exemplary heater bodies c100, while FIG. 4.1.4schematically depicts a top view of the exemplary heater body c100 shownin FIG. 4.1.3A. As shown, an exemplary heater body c100 may have anannular configuration, however, other configurations are alsocontemplated. The heater body c100 may include a plurality of monolithicbody portions that together may define a monolithic heater body c100.Alternatively, or in addition, the heater body c106 may include one ormore monolithic body-segments operably coupled or operably couplable toa monolithic heater body c100. Further, a plurality of monolithicbody-segments may be operably coupled or operably couplable to oneanother to define at least a portion of a heater body c100. In anexemplary embodiment, a heater body c100 may define a single monolithicbody. In other embodiments, a plurality of monolithic body-segments maybe operably coupled to one another, such as via welding, fusing, or thelike, so as to provide an integrally formed heater body c100.

A heater body c100 and/or various featured thereof may include aproximal portion c200 and a distal portion c202 oriented relative to alongitudinal axis c204, with a medial portion c206 disposed between theproximal portion c200 and the distal portion c202. The proximal portionc200 of the heater body c100 or a feature thereof refers to a portion,relative to a longitudinal axis c204, adjacent or relatively proximateto a working-fluid body c108 such as one or more pistons of aclosed-cycle engine c002. The distal portion c202 of the heater bodyc100 or a feature thereof refers to a portion, relative to thelongitudinal axis c204, opposite from or relatively remote to theworking-fluid body c108. A proximal, distal, or medial portion c200,c202, c206 need not refer to a finite point on the heater body c100 or afeature thereof; rather, it will be appreciated that the terms proximal,distal, and medial c200, c202, c206 may be used generally, such as todenote the location of a portion of the heater body c100 or a featurethereof relative to the working-fluid body c108 and/or to denote thelocation of various features of the heater body c100 relative to oneanother.

Referring still to FIGS. 4.1.3A, 4.1.3B, and 4.1.3C, a heater body c100may include a combustion chamber c102 and a hot-side heat exchanger c106circumferentially surrounding at least a portion of the combustionchamber c102. In some embodiments, a recirculation pathway c104 maycircumferentially surround at least a portion of the combustion chamberc102. A heater body c100 may additionally or alternatively include aconditioning conduit c122 circumferentially surrounding at least aportion of the combustion chamber c102. For example, as shown, thehot-side heat exchanger c106 may circumferentially surround a proximalportion c200 of the combustion chamber c102 and the conditioning conduitc122 may circumferentially surround a medial portion c206 and/or adistal portion c202 of the combustion chamber c102. In some embodiments,the hot-side heat exchanger c106 may additionally circumferentiallysurround at least some of a medial portion c206 of the combustionchamber c102. In some embodiments, it may be advantageous for thecombustion chamber c102 to be aligned with the longitudinal axis c204and/or for a plurality of combustion chambers c102 to becircumferentially spaced (e.g., evenly distributed) about thelongitudinal axis c204. For example, such alignment and/or evendistribution may encourage relatively even heat distribution within theheater body c100 and/or the hot-side heat exchanger c106. Suchrelatively even heat distribution may, in turn, encourage relativelyeven heat transfer from the hot-side heat exchanger c106 (e.g., from aheating fluid flowing therethrough) to the plurality of heat transferregions.

The heater body c100 may further include a recirculation eductor c116circumferentially surrounding the combustion chamber c102. When theheater body c100 includes a conditioning conduit c122, the recirculationeductor c116 may be disposed radially or concentrically outward from theconditioning conduit c122, for example, such that the recirculationeductor c116 circumferentially surrounds at least a portion of theconditioning conduit c122. For example, the recirculation eductor c116may circumferentially surround a distal portion c202 and/or a medialportion (e.g., a distally-medial portion) of the combustion chamberc102. Additionally, when the heater body c100 includes a conditioningconduit c122, the recirculation eductor c116 may circumferentiallysurround a distal portion c202 and/or a medial portion (e.g., adistally-medial portion) of the conditioning conduit c122. Therecirculation eductor c116 may be disposed axially adjacent to thehot-side heat exchanger c106, such as adjacent to a distal portion c202of the hot-side heat exchanger c106 relative to the longitudinal axisc204.

In some embodiments, a heater body c100 may include a heat recuperatorc124 circumferentially surrounding the combustion chamber c102. When theheater body c100 includes a conditioning conduit c122, the heatrecuperator c124 may be disposed radially or concentrically outward fromthe conditioning conduit c122, for example, such that the heatrecuperator c124 circumferentially surrounds at least a portion of theconditioning conduit c122. For example, the heat recuperator c124 maycircumferentially surround a distal portion c202 and/or a medial portion(e.g., a distally-medial portion) of the combustion chamber c102.Additionally, when the heater body c100 includes a conditioning conduitc122, the heat recuperator c124 may circumferentially surround a distalportion c202 and/or a medial portion (e.g., a distally-medial portion)of the conditioning conduit c122. The heat recuperator c124 may bedisposed axially adjacent to the recirculation eductor c116, such asadjacent to a distal portion c202 of the recirculation eductor c116relative to the longitudinal axis c204.

In some embodiments, as shown for example in FIG. 4.1.3B, a heater bodyc100 may include a heat shield c127. The heat shield c127 may beconfigured to insulate and/or shield one or more portions of the heaterbody c100 from a heat source within the heater body c100. For example,the heat source may include a combustion flame and/or combustion gascirculating through the recirculation pathway c104, and/or portions ofthe heater body c100 that become heated by the combustion flame and/orcombustion gas. Additionally, or in the alternative, the heat shieldc127 may provide a heat sink to absorb and/or dissipate heat, such asheat from a combustion flame and/or combustion gas circulating throughthe recirculation pathway c104. In some embodiments, the heat shieldc127 may include a cooling jacket c128 defined by an inner wall c130 andan outer wall c132. The cooling jacket c128 may fluidly communicate withthe intake air annulus c216, such that intake air may flow therethrough.Additionally, or in the alternative, the cooling jacket c128 may definea space with a vacuum or near vacuum. The cooling jacket c128 may defineone or more pathways, such as an annular pathway or a plurality ofsemi-annular pathways. The cooling jacket may cool hot portions of theheater body c100, for example to maintain suitable operatingtemperatures and/or to shield users or surrounding equipment from hotportions of the heater body c100.

A heater body c100 may define a single monolithic body providing arecirculation pathway c104, an intake air pathway c118, and/or anexhaust pathway c120. For example, a plurality of monolithic bodyportions may together define a single monolithic body. Alternatively, aheater body c100 may include separate monolithic body-segmentsrespectively defining a recirculation pathway c104, an intake airpathway c118, and/or an exhaust pathway c120. In some embodiments, afirst monolithic body-segment may define a recirculation pathway c104, asecond monolithic body-segment may define an intake air pathway c118,and a third monolithic body-segment may define an exhaust pathway c120.Such monolithic body-segments may be coupled to one another, such as viawelding, fusing, or the like, so as to provide an integrally formedheater body c100.

A monolithic body defining a recirculation pathway c104 may include acombustion chamber c102 and a hot-side heat exchanger c106 fluidlycommunicating with a proximal portion c200 of the combustion chamberc102. Such a monolithic recirculation pathway c104 may additionallyinclude a recirculation eductor c116 fluidly communicating with aradially or concentrically outward portion of the hot-side heatexchanger c106 and a conditioning conduit c122 having a proximal portionc200 fluidly communicating with a radially or concentrically inwardportion of the recirculation eductor c116 and a distal portion c202fluidly communicating with a distal portion c202 of the combustionchamber c102.

In some embodiments, a heater body c100 may include a recirculationannulus c208. The recirculation annulus c208 may be disposed radially orconcentrically outward from at least a portion of the hot-side heatexchanger c106 and/or at least a portion of the recirculation eductorc116. Additionally, or in the alternative, the recirculation annulusc208 may circumferentially surround at least a portion of the hot-sideheat exchanger c106 and/or at least a portion of the recirculationeductor c116. The recirculation annulus c208 may fluidly communicatewith a radially or concentrically outward portion of the hot-side heatexchanger c106 and a radially or concentrically outward portion of therecirculation eductor c116 so as to define a pathway to direct at leasta portion of the combustion gas discharging from the hot-side heatexchanger c106 into the recirculation annulus c208.

In some embodiments, a heater body c100 may include fuel injector bodyc401. The fuel injector body c401 may include a combustor cap c210providing fluid communication between a distal portion c202 of theconditioning conduit c122 and a distal portion c202 of the combustionchamber c102. The fuel injector body c401 may additionally oralternatively include one or more fuel nozzles c214. The fuel injectorbody c401 and/or the combustor cap c210 and/or one or more fuel nozzlesc214 may be a separate component operably coupled or operably couplableto the heater body c110, such as at a distal portion c202 of theconditioning conduit c122 as shown. Additionally, or in the alternative,the fuel injector body c401 and/or the combustor cap c210 and/or one ormore fuel nozzles c214 may be a portion of a monolithic body defining atleast a portion of the heater body c100.

In some embodiments, one or more fuel nozzles c214 may be operablycoupled to the combustor cap c210. For example, the combustor cap c210may include one or more nozzle ports c212 respectively configured toreceive a fuel nozzle c214. One or more fuel nozzles c214 may beoperably coupled to corresponding nozzle ports c212 such as by matingthreads or the like. The one or more fuel nozzles c214 may include aglow plug c215 operable to ignite fuel and/or combustion gas in thecombustion chamber c102. As shown, the fuel nozzle may be aligned withthe longitudinal axis c204 of the heater body c100 and may be concentricwith the combustion chamber c102. Additionally, or in the alternative,one or more fuel nozzles c214 may be circumferentially spaced about thedistal portion c202 of the combustion chamber. In some embodiments, itmay be advantageous for a fuel nozzle c214 to be aligned with thelongitudinal axis c204 and/or for a plurality of fuel nozzles c214 to becircumferentially spaced (e.g., evenly distributed) about thelongitudinal axis c204. For example, such alignment and/or evendistribution may encourage flame stability within the combustion chamberc102 and/or relatively even heat distribution within the combustionchamber c102 and/or the hot-side heat exchanger c106.

A monolithic body defining an intake air pathway c118 may include anintake air body, such as an intake air annulus c216 and/or a monolithicbody defining an exhaust pathway c120 may include an exhaust body, suchas an exhaust annulus c218. The intake air annulus c216 and the exhaustannulus c218 may define portions of a single monolithic body or may beseparate monolithic body-segments operably coupled or operably couplableto one another. The intake air annulus c216 and/or the exhaust annulusc218 may circumferentially surround at least a portion of the combustionchamber c102. As shown, the intake air annulus c216 may include one ormore intake ports c220 and the exhaust annulus c218 may include one ormore exhaust ports c222. As shown in FIGS. 4.1.3A and 4.1.3B, the intakeair annulus c216 and the exhaust annulus c218 may be disposed axiallyadjacent to one another. For example, the intake air annulus c216 may beadjacent to a distal portion c202 of the exhaust annulus c218 and/or theexhaust annulus c218 may be adjacent to a proximal portion of the intakeair annulus c216 relative to the longitudinal axis c204. As shown inFIG. 4.1.3C, the intake air annulus c216 and the exhaust annulus c218may be disposed co-annularly relative to one another. For example, theintake air annulus c216 may be disposed radially or concentricallyinward from the exhaust annulus c218, with the exhaust annulus c218circumferentially surrounding the intake air annulus c216.Alternatively, the exhaust annulus c218 may be disposed radially orconcentrically inward from the intake air annulus c216, with the intakeair annulus c216 circumferentially surrounding the exhaust annulus c218.

The intake air annulus c216 may include a plurality of intake vanes c224circumferentially spaced about the intake air annulus c216. The intakevanes c224 may define at least a portion of a pathway configured todirect intake air from the intake air annulus c216 to the recirculationpathway c104. The exhaust annulus c218 may include a plurality ofexhaust vanes c226 circumferentially spaced about the exhaust annulusc218. The exhaust vanes c226 may define at least a portion of a pathwayconfigured to direct exhaust gas into the exhaust pathway c218.

In some embodiments, the intake air annulus c216 and the exhaust annulusc218 may fluidly communicate with a heat recuperator c124. Moreparticularly, a preheater portion of the heat recuperator c124 maydefine at least a portion of an intake air pathway c118 and arecuperator portion of the heat recuperator c124 may define at least aportion of an exhaust pathway c120. The heat recuperator c124 may bepart of a monolithic body defining the intake air pathway c118 and/orthe exhaust pathway c120. The exhaust annulus c218 and/or the intake airannulus c216 may circumferentially surround at least a portion of theheat recuperator c124. As shown in FIG. 4.1.2A, the exhaust annulus c218may circumferentially surround the heat recuperator c124, and the intakeair annulus c216 may be axially adjacent to the exhaust annulus c218,with the intake vanes c224 being axially adjacent to at least a portionof the heat recuperator c124. For example, the intake vanes c224 may beadjacent to a distal portion c202 of the heat recuperator c124.

The heat recuperator c124 may include a preheater portion and arecuperator body portion having a thermally conductive relationship withone another. The preheater portion may fluidly communicate with theintake air annulus c216 and the recirculation eductor c116 so as todefine at least a portion of the intake air pathway c118. Therecuperator body portion may fluidly communicate with the recirculationeductor c116 and the exhaust annulus c218 so as to define at least aportion of the exhaust pathway c120. In an exemplary embodiment, theexhaust pathway c120 from the recirculation eductor c116 may be upstreamfrom the intake air pathway c118 to the recirculation eductor c116 so asto avoid intake air from the intake air pathway c118 flowing directlyinto the exhaust pathway c120 before combining with the recirculationpathway c104.

In some embodiments, a heater body c100 may include a motive annulusc228 providing fluid communication from the preheater portion of therecuperator c124 to the recirculation eductor c116. The heat recuperatorc124 may circumferentially surround the motive annulus c228, and themotive annulus may circumferentially surround at least a portion of thecombustion chamber c102. When the heater body c100 includes aconditioning conduit c122, the motive annulus c228 may be disposedradially or concentrically outward from the conditioning conduit c122,for example, such that the motive annulus c228 circumferentiallysurrounds at least a portion of the conditioning conduit c122. Forexample, the motive annulus c228 may circumferentially surround a medialportion of the combustion chamber c102 and/or a medial portion of theconditioning conduit c122. The motive annulus c228 may be disposedaxially adjacent to the recirculation eductor c116, such as adjacent toa distal portion of the recirculation eductor c116 relative to the axialaxis c204.

In exemplary embodiments, the recirculation pathway c104, the intake airpathway c118 and/or the exhaust pathway c120 may follow a generallyspiral orientation. As shown in FIG. 4.1.2A, the recirculation pathwayc104 and the intake air pathway c118 may spiral counterclockwise, andthe exhaust pathway c120 may spiral clockwise. Alternative, therecirculation pathway c104 and the intake air pathway c118 may spiralclockwise, and the exhaust pathway c120 may spiral counterclockwise.Such flows through the heater body c100 may transition fromcounterclockwise flow to clockwise flow (or from clockwise flow tocounterclockwise flow) at the exhaust pathway c120, where exhaust gasseparates from combustion gas at the recirculation eductor c116. In thisway, pressure loss from a change in flow direction may be minimized.Additionally, a pressure drop associated with a change in direction atthe exhaust pathway c120 may at least partially favor recirculation ofcombustion gas through the recirculation eductor c116.

During operation, intake air is directed into the intake air annulusc216. In some embodiments, the intake air may be pressurized, such asvia a compressor (not shown), to induce a flow of intake air into theintake air pathway c118. The intake air circulates counterclockwisethrough the intake air annulus c216, where a plurality of intake vanesc224 circumferentially spaced about the intake air annulus c216 directthe intake air in a radially or concentrically inward and axiallyproximal spiral having a counterclockwise orientation. The intake airflowing through the intake vanes c224 continues a radially orconcentrically inward spiral flow through the heat recuperator c124 andinto the motive annulus c228. The intake air in the motive annulus c228enters the recirculation eductor c116 through a plurality of eductorslots configured to accelerate the intake air spirally into theconditioning conduit c122. The intake air passing through the eductorslots accelerates and entrains combustion gas flowing into therecirculation eductor c116 from the recirculation annulus c208. Theintake air and the combustion gas mix to provide fresh combustion gaswhile flowing helically through the conditioning conduit c122 in anaxially distal direction. The fresh combustion gas reaches thecombustion cap c210, which directs the flow of fresh combustion gas intothe combustion chamber while a fuel nozzle c214 introduces a flow offuel, which may include a liquid, gaseous fuel.

In the combustion chamber c102, fuel combines with the fresh combustiongas and is ignited, for example, by a glow plug or a spark plug. Thecombustion chamber c102 provides a vortex combustion pattern with acounterclockwise flow. Centripetal force of the vortex combustionpattern draw the combustion flame radially or concentrically inwardwhile propelling unburnt combustion gas radially or concentricallyoutward. The combustion gas continues with a spiral counterclockwiseflow out of the combustion chamber c102 and into the hot-side heatexchanger c106. The combustion gas flows in a radially or concentricallyoutward counterclockwise spiral through the hot-side heat exchanger c106and into the recirculation annulus c208.

The recirculation annulus c208 directs the combustion gas in an axiallydistal and radially or concentrically inward direction into therecirculation eductor c116, where a portion of the combustion gas isaccelerated and entrained by intake air flowing through the eductorslots of the recirculation eductor c116. The remainder of the combustiongas flows in an axially distal direction through exhaust slots in therecirculation eductor c116. The exhaust slots in the recirculationeductor c116 reverse the direction of the exhaust gas flow, directingthe exhaust gas in an axially distal and clockwise spiral direction intothe recuperator body portion of the heat recuperator c124. The exhaustgas flow in a clockwise spiral into the exhaust annulus c218, where theexhaust gas discharges from the heater body c100 through one or moreexhaust ports c222.

Referring still to e.g., FIGS. 4.1.2A and 4.1.2B, and 4.1.3A through4.1.3C, an exemplary heater body c100 may include a combustion chamberc102 and a recirculation pathway c104 configured to recirculatecombustion gas through the combustion chamber c102. The heater body c100includes an intake air pathway c118 and an exhaust pathway c120 mayfluidly communicate with the recirculation pathway c104. Therecirculation pathway c104 may include a hot-side heat exchanger c106and a recirculation eductor c116. However, in some embodiments, therecirculation eductor c116 may be omitted and the combustion chamberc102 may fluidly communicate with the intake air pathway c118 and theexhaust pathway c120 with combustion gas discharging from the heaterbody without recirculating. The exhaust pathway c120 may fluidlycommunicate with the recirculation pathway c104 upstream from the intakeair pathway c118.

As shown in FIGS. 4.1.2A and 4.1.3A, the hot-side heat exchanger c106may fluidly communicate with a proximal portion of the combustionchamber c102, and the recirculation eductor c116 may fluidly communicatewith a downstream portion of the hot-side heat exchanger c106 and adistal portion c202 of the combustion chamber c102. The recirculationeductor c116 may be configured to entrain and/or accelerate combustiongas circulating through the recirculation pathway c104 using intake air,for example, from an intake air pathway c118 may fluidly communicatewith the recirculation pathway c104.

In some embodiments, the recirculation eductor c116 may define at leasta portion of the exhaust pathway c120. For example, the exhaust pathwayc120 may fluidly communicate with the recirculation pathway c104 at therecirculation eductor c116, such that the exhaust pathway c120discharges a portion of the combustion gas from the recirculationeductor c116 as exhaust gas. In another embodiment, as shown for examplein FIG. 4.1.2B, the exhaust pathway c120 may discharge exhaust gasupstream from the recirculation eductor c116.

When the heater body c100 includes a recirculation pathway c104, theproportion of combustion gas may be recirculated may vary depending onthe operating conditions of the heater body c100. The proportion ofcombustion gas may be recirculated to the proportion of fresh intake airmay be utilized may be described by a recirculation ratio R, accordingto the following equation (1): R=I/C, where I is the flow rate if intakeair flowing into the heater body c100 and T is C the flow rate ofcombustion gas flowing to the combustion chamber. The recirculationratio may vary from 0% to 100% depending, for example, on the operatingconditions of the heater body c100. For example, a greater proportion ofintake air may be utilized during startup, with recirculation ratioincreasing as the heater body c100 transitions from startup conditionsto steady-state conditions. Additionally, the recirculation ratio maydepend on desired combustion conditions, such as equivalence ratio. Insome embodiments, the recirculation ratio may be from 0% to 90%, such asfrom 10% to 90%, such as from 0% to 60%, such as from about 30% to about70%, such as from 40% to 60%. During startup conditions, therecirculation ratio may be from 0% to 50%, such as from 0% to 30% orfrom 0% to 10%. During steady-state conditions, the recirculation ratiomay be from 10% to 90%, such as from 10% to 60%, or from 30% to 60%. Theremainder of combustion gas may be discharged from the recirculationpathway c104 as exhaust gas.

In some embodiments, the exemplary heater body c100 may include a heatrecuperator c124 defining at least a portion of an exhaust pathway c120and at least a portion of an intake air pathway c118. The heatrecuperator c124 may be located upstream from a recirculation eductorc116 as shown in FIG. 4.1.2A, or the heat recuperator c124 may belocated upstream from a recirculation eductor c116 as shown in FIG.4.1.2B. As shown in FIG. 4.1.2A, the heat recuperator c124 may utilizeexhaust gas flowing through the exhaust pathway c120 to preheat intakeair flowing through the intake air pathway c118, the exhaust pathwayc120 having a thermally conductive relationship with the intake airpathway c118. The heat recuperator c124 may fluidly communicate with therecirculation pathway c104 indirectly, such as at the recirculationeductor c116 through the exhaust pathway c120 and the intake air pathwayc118. Alternatively, the heat recuperator c124 may fluidly communicatewith the recirculation pathway c104 directly, as shown in FIG. 4.1.2A,such that the heat recuperator c124 may heat the intake using combustiongas recirculating through the recirculation pathway c104 to air, or acombination of exhaust gas and combustion gas. Regardless of whether theheat recuperator c124 utilizes exhaust gas and/or recirculatingcombustion gas to heat the intake air, the exhaust pathway c120 may belocated upstream from the intake air pathway c118, such that exhaust gasmay be removed from the recirculation pathway c104 prior to intake airbeing introduced to the recirculation pathway c104.

Now referring to FIG. 4.1.5 exemplary methods of heating a heatexchanger body c600 will be described. The exemplary methods of heatinga heat exchanger body c600 may include, for example, methods of heatinga closed-cycle engine c002. For example, exemplary methods may beperformed in connection with operation of a heater body c100 and/or aclosed-cycle engine c002 as described herein. As shown in FIG. 4.1.5, anexemplary method c150 may include, at block c152, circulating combustiongas through a combustion chamber c102 and a recirculation pathway c104configured to recirculate combustion gas through the combustion chamberc102. The recirculation pathway c104 may include a hot-side heatexchanger c106 and a recirculation eductor c116. The hot-side heatexchanger c106 may fluidly communicate with a proximal portion of thecombustion chamber c102. The recirculation eductor c116 may fluidlycommunicate with a downstream portion of the hot-side heat exchangerc106 and a proximal portion of the conditioning conduit c122 and/or anda distal portion of the combustion chamber c102. At block c154, anexemplary method c150 may include transferring heat from the combustiongas in the hot-side heat exchanger c106 to a plurality of heat transferregions that respectively have a heat transfer relationship with acorresponding semiannular portion of the hot-side heat exchanger c106.The exemplary method c150 may include, at block c156, swirlingcombustion gas through a conditioning conduit c122 defining at least aportion of the recirculation pathway c104. The conditioning conduit c122may fluidly communicate with a downstream portion of the recirculationeductor c116 and a distal portion of the combustion chamber c102. Theexemplary method c150 may additionally include, at block c158,combusting a fuel and/or at least a portion of the combustion gas. Thefuel and/or combustion gas may be combusted in the combustion chamberc102. In some embodiments, at least a portion of the combustion may takeplace within the hot-side heat exchanger c106.

In some embodiments, an exemplary method c150 may include, at blockc160, injecting intake air into the recirculation pathway c104. Theintake air may be injected through an intake air pathway c118 fluidlycommunicating with the recirculation pathway c104. For example, arecirculation eductor c116 may include a motive pathway defining atleast a portion of the intake air pathway c118. The exemplary method mayadditionally include, at block c162, entraining and/or acceleratingcombustion gas circulating through the recirculation pathway c104 atleast in part by injecting the intake air into the recirculation pathwayc104, for example, through the motive pathway of the recirculationeductor c116. The exemplary method may further include, at block c164,discharging a portion of the combustion gas from the recirculationpathway c104 as exhaust gas. The exhaust gas may discharge through anexhaust pathway c120, and the exhaust gas pathway c120 may fluidlycommunicate with the recirculation pathway c104. In some embodiments,the exhaust gas pathway c120 may be defined at least in part by therecirculation eductor c116. The exhaust gas may be preferentiallydischarged from the recirculation pathway c104 upstream from a locationwhere the intake air pathway c118 fluidly communicates with therecirculation pathway c104.

The exemplary method may additionally include, at block c166, preheatingintake air flowing through the intake air pathway c118. The intake airmay be preheated at least in part using exhaust gas flowing through anexhaust pathway c120 by the exhaust pathway c120 having a thermallyconductive relationship with the intake air pathway c118. For example,in some embodiments, the intake air may be preheated at least in partusing a heat recuperator c124. The heat recuperator c124 may define atleast a portion of the intake air pathway c118 and at least a portion ofthe exhaust pathway c120, thereby providing a thermally conductiverelationship between the exhaust gas pathway c120 and the intake airpathway c118. Additionally, or in the alternative, the intake air may bepreheated at least in part using combustion gas flowing through arecirculation pathway c104 by the recirculation pathway c104 having athermally conductive relationship with the intake air pathway c118. Withthe heat recuperator c124 fluidly communicating with the recirculationeductor c116, the exemplary method c150 may include flowing combustiongas from the recirculation pathway c104 into the heat recuperator c124at the recirculation eductor c116 through the exhaust pathway c120, andflowing intake air from the intake air pathway c118 into therecirculation eductor c116 at the heat recuperator c124. The exhaustpathway c120 may preferably be located upstream from the intake airpathway c118.

In an exemplary embodiment, transferring heat from the combustion gas inthe hot-side heat exchanger c106 at block c154 may include transferringheat to a working-fluid body c108. The working-fluid body c108 mayinclude a solid body and/or fluid in a fluid pathway defined at least inpart by the solid body. The heat transferring to the working-fluid bodyc108 may come from combustion gas flowing through a plurality of heatingfluid pathways defined at least in part by the hot-side heat exchangerc106. The heat may be transferred to respective ones of a plurality ofheat transfer regions that have a thermally conductive relationship witha corresponding portion of the plurality of heating fluid pathways. Theworking-fluid body c108 may include a plurality of working-fluidpathways, and the exemplary method c150 may include flowing fluidthrough the working-fluid pathways as heat transfers thereto from thehot-side heat exchanger c106. In some embodiments, the working-fluidpathways may fluidly communicate with a piston chamber and a regeneratorof a closed-cycle engine c002, and the exemplary method may includeflowing fluid through the working-fluid pathways alternatingly betweenthe regenerator and the piston chamber.

In an exemplary embodiment, combusting a fuel and/or at least a portionof the combustion gas at block c158 may include combusting fuel and atleast a portion of the combustion gas in the combustion chamber c102and/or in the heating fluid pathways of the hot-side heat exchangerc106. The fuel may be supplied by a fuel nozzle fluidly communicatingwith the combustion chamber c102. The combustion gas circulating throughthe combustion chamber c102 and/or the recirculation pathway c104 atblock c152 may be from 10% to 90% of the total combustion gas flowinginto the combustion chamber c102, and the remainder of the combustiongas may be discharged from the recirculation pathway c104 as exhaust gasthrough the exhaust pathway c120. It will be appreciated that theproportion of combustion gas being recirculated may vary depending onoperating conditions and/or configuration of the heater body c100. Forexample, the proportion of combustion gas being recirculated may vary asbetween startup and steady-state conditions. Also, in some embodiments,the heater body c100 may not have a recirculation pathway or therecirculation pathway may be closed so as to carry out combustion of thefuel utilizing 100% intake air.

Now referring to FIGS. 4.1.6A and 4.1.6B exemplary monolithic bodiesdefining at least a portion of a heater body c100 will be described.Exemplary monolithic bodies may be formed as one single monolithic body.Various portions of a monolithic body are sometimes referred to asmonolithic body portions. Additionally, or in the alternative, exemplarymonolithic bodies may include a plurality of segments combinable to forma monolithic body. Such segments are sometimes referred to herein asmonolithic body-segments. As shown in FIGS. 4.1.6A and 4.1.6B, anexemplary heater body c100 may include a combustor body c400, a fuelinjector body c401, a hot-side heat exchanger body c600, an eductor bodyc300, a heat recuperator body c500, and/or a working-fluid body c108.The combustor body c400, the fuel injector body c401, the hot-side heatexchanger body c600, the eductor body c300, the heat recuperator bodyc500, and/or the working-fluid body c108 may respectively definemonolithic body portions of the heater body c100 and/or monolithicbody-segments of the heater body c100.

An exemplary heater body c100 may include a combustor body c400. Thecombustor body c400 may include a combustion chamber body c402 definingat least a portion of a combustion chamber c102. The combustion chamberbody c402 and/or the combustion chamber c102 may be disposed annularlyabout an axis c204. The combustor body c400 may additionally include aconditioning conduit body c404 defining at least a portion of aconditioning conduit c122 circumferentially surrounding the combustionchamber c102. The combustion chamber body c402 and the conditioningconduit body c404 may be monolithically integrated with the heater bodyc100 at a distal portion of the heater body c100 such that theconditioning conduit may fluidly communicate with the combustion chamberc102 at a distal portion of the combustion chamber c102. For example,the conditioning conduit body c404 may be monolithically integrated withthe combustion chamber body c402. Alternatively, the combustion chamberbody c402 and the conditioning conduit body c404 may define monolithicbody-segments operably couplable to one another and/or to the heaterbody c100 or another monolithic body-segment thereof so as to provide anintegrally formed combustor body c400.

An exemplary heater body c100 may additionally or alternatively includea fuel injector body c401. The fuel injector body c401 may bemonolithically integrated with the heater body c100 at a distal portionc202 of the heater body c100, such as at a distal portion c202 of thecombustion chamber c102. For example, the fuel injector body c401 may bemonolithically integrated with the combustor body c400 (e.g., with thecombustion chamber body c402 and/or the conditioning conduit body c404).Alternatively, the fuel injector body c401 and the combustor body c400(e.g., the combustion chamber body c402 and/or the conditioning conduitbody c404) may define monolithic body-segments operably couplable to oneanother and/or to the heater body c100 or another monolithicbody-segment thereof.

An exemplary heater body c100 may additionally or alternatively includea hot-side heat exchanger body c600. The hot-side heat exchanger bodyc600 may include a plurality of heating fluid pathways and a pluralityof heat transfer regions. The plurality of heating fluid pathways may becircumferentially spaced about an inlet plenum fluidly communicatingwith the plurality of heating fluid pathways. In some embodiments,respective ones of the plurality of heating fluid pathways may define aspiral pathway. Respective ones of the plurality of heat transferregions may have a heat transfer relationship with a correspondingsemiannular portion of the plurality of heating fluid pathways.

The hot-side heat exchanger body c600 may be monolithically integratedwith the heater body c100 at a proximal portion c200 of the heater bodyc100 such that the combustion chamber c102 may fluidly communicate withthe plurality of heating fluid pathways at a proximal portion c200 ofthe combustion chamber c102. For example, the hot-side heat exchangerbody c600 may be monolithically integrated with the combustor body c400(e.g., with the combustion chamber body c402 and/or the conditioningconduit body c404). Alternatively, the hot-side heat exchanger body c600and the combustor body c400 (e.g., the combustion chamber body c402and/or the conditioning conduit body c404) may define monolithicbody-segments operably couplable to one another and/or to the heaterbody c100 or another monolithic body-segment thereof.

An exemplary heater body c100 may additionally or alternatively includean eductor body c300. The eductor body c300 may be monolithicallyintegrated with the hot-side heat exchanger body c600 and/or thecombustor body c400 (e.g., the conditioning conduit body c404) such thatthe plurality of heating fluid pathways may fluidly communicate with aradially or concentrically outward portion of the an eduction pathwaydefined by the eductor body c300. In some embodiments, the exemplaryheater body c100 may include a recirculation annulus body c302configured to provide fluid communication between the plurality ofheating fluid pathways of the hot-side heat exchanger body c600 and thecombustor body c400 (e.g., the conditioning conduit body c404).

An exemplary heater body c100 may additionally or alternatively includea heat recuperator body c500. The heat recuperator body c500 may bemonolithically integrated with the eductor body c300. In someembodiments, the exemplary heater body c100 may include an intakeannulus body c502, an exhaust annulus body c504, and/or a motive annulusbody c506. The intake annulus body c502 may be monolithically integratedwith the heat recuperator body c500 such that the intake annulus bodyc502 and the heat recuperator body c500 define at least a portion of anintake air pathway c118. The exhaust annulus body c504 may bemonolithically integrated the heat recuperator body c500 such that theexhaust annulus body c504 and the heat recuperator body c500 define atleast a portion of the exhaust pathway c120. The motive annulus bodyc502 may be monolithically integrated with the heat recuperator bodyc500 and the eductor body c300 such that the motive annulus body definesat least a portion of the intake air pathway c118 between the heatrecuperator body c500 and the eductor body c300.

An exemplary heater body c100 may additionally or alternatively includea working-fluid body c108. A working-fluid body c108 may include any oneor more bodies that receive a heat input from the hot-side heatexchanger body c600. An exemplary working-fluid body c108 may includeone or more piston bodies c700 and/or one or more regenerator bodiesc800. An exemplary working-fluid body c108 may additionally oralternatively include one or more working-fluid pathways c110, such asone or more working-fluid pathways c110 fluidly communicating with atleast one piston body c700 and/or at least one regenerator body c800. Aworking-fluid body c108 may be monolithically integrated with thehot-side heat exchanger body c600. In some embodiments, theworking-fluid body c108 may define at least a portion of a plurality ofworking-fluid pathways. Additionally, or in the alternative, in someembodiments the hot-side heat exchanger body c600 may define at least aportion of the plurality of working-fluid pathways.

As shown in FIG. 4.1.6B, an exemplary monolithic body may include aplurality of monolithic body-segments. A heater body c100 may includeany one or more of the elements described with reference to FIG. 4.1.6Aprovided as a monolithic body portion or as a monolithic body-segment.An exemplary heater body c100 may include an arrangement of monolithicbody-segments as shown in FIG. 4.1.6B; however, other combinations andarrangements are contemplated and any combination or arrangement ofmonolithic body-segments is within the scope of the present disclosure.As shown in FIG. 4.1.6B, a heater body c100 may include a firstmonolithic body-segment c056, a second monolithic body-segment c058, anda third monolithic body-segment c060.

The first monolithic body-segment c056 may include a combustor bodyc400. Additionally, or in the alternative, the first monolithicbody-segment c056 may include a fuel injector body c401. The secondmonolithic body-segment c058 may include an eductor body c300 defining afirst monolithic body portion of the second monolithic body-segmentc058, a heat recuperator body c500 defining a second monolithic bodyportion of the second monolithic body-segment c058, a recirculationannulus body c302 defining a third monolithic body portion of the secondmonolithic body-segment c058, an intake annulus body c502 defining afourth monolithic body portion of the second monolithic body-segmentc058, an exhaust annulus body c506 defining a fifth monolithic bodyportion of the second monolithic body-segment c058, and/or a motiveannulus body c506 defining a sixth monolithic body portion of the secondmonolithic body-segment c058, as well as subcombinations of these.

The third monolithic body-segment c060 may include a hot-side heatexchanger body c600 defining a second monolithic body portion of thethird monolithic body-segment c060, and a working-fluid body c108defining a second monolithic body portion of the third monolithicbody-segment c060. In other embodiments, the first monolithicbody-segment c056, the second monolithic body-segment c058, and/or thethird monolithic body-segment c058 may respectively include anysubcombination of the foregoing monolithic body portions, respectivelyprovided as monolithic body portions of a respective monolithicbody-segment or as separate monolithic body-segments.

Now referring to FIGS. 4.1.7, 4.1.8A-4.1.8G, 4.1.9, and 4.1.10, furtherexemplary embodiments will be described that pertain to a heater bodyc100, such as a monolithic heater body c100, and/or to one or moremonolithic body-segments that make up the heater body c100. A heaterbody c100 and/or a monolithic body-segment may include one or morefeatures that allow the heater body c100 to operate at a relativelyelevated temperature. For example, such features may include one or moreheat shields c127, one or more heat-capture pathways c133, and/or one ormore thermal expansion joints c135, as respectively described herein.Such features may allow for a closed cycle engine such as a Sterlingengine to operate at with an improved temperature ratio(THot,engine/TCold,ambient) and/or with an improved Carnot efficiency.For example, in some embodiments, a closed cycle engine that includes aheater body c100 configured in accordance with the present disclosuremay exhibit a temperature ratio of from about 2 to about 4, such as atleast about 2, such as at least about 3, or such as at least about 3.5.Additionally, or in the alternative, a closed cycle engine that includesa heater body c100 configured in accordance with the present disclosuremay exhibit an improved Carnot efficiency, such as a Carnot efficiency40% to about 60%, such as from about 50% to about 70%, such as fromabout 60% to about 70%, such as from about 60% to about 80%; such as atleast about 50%, such as at least about 60%, such as at least about 65%.Such improved temperature ratio and/or improved Carnot efficiency may beattributable at least in part to the heater body c100 being configuredaccording to the present disclosure. By way of example, the one or moreheat shields c127, the one or more heat-capture pathways c133, and/orthe one or more thermal expansion joints c135, may allow the heater bodyc100 to operate at an elevated temperature, thereby increasing thetemperature difference between a hot side and a cold side of a heatengine, and corresponding conversation of heat energy to mechanicalwork, effective to impart such temperature ratio and/or such Carnotefficiency.

In some embodiments, a one or more portions of a monolithic heater bodyc100, and/or to one or more monolithic body-segments that make up theheater body c100, may include a heat shield c127. The heat shield c127may be configured to insulate and/or shield one or more portions of theheater body c100 from a heat source within the heater body c100. Forexample, the heat source may include a combustion flame and/orcombustion gas circulating through the recirculation pathway c104,and/or portions of the heater body c100 that become heated by thecombustion flame and/or combustion gas. Additionally, or in thealternative, the heat shield c127 may provide a heat sink to absorband/or dissipate heat, such as heat from a combustion flame and/orcombustion gas circulating through the recirculation pathway c104. FIG.4.1.7 shows a variety of exemplary locations for a heat shield c127.

As shown, in some embodiments, a heat shield c127 may be disposed aboutan exterior region of a heater body c100. For example, a first heatshield c127A may circumferentially surround at least a portion of ahot-side heat exchanger c106 and/or at least a portion of aworking-fluid body c108, such as an outward portion of a hot-side heatexchanger c106 and/or an outward portion of a working-fluid body c108.The first heat shield c127A may be disposed about an annular orsemi-annular portion of the hot-side heat exchanger c106, and/or anannular or semi-annular portion of the working-fluid body c108.

Additionally, or in the alternative, a second heat shield c127B may bedisposed about an inward portion of a heater body c100, such as aninward annular portion of a heater body c100 or an inward semi-annularportion of a heater body c100. As shown, the second heat shield c127Bmay be disposed about an inward annular or semiannular portion of ahot-side heat exchanger c106 and/or working-fluid body c108. The secondheat shield c127B may be additionally or alternatively disposed about aradial portion of the hot-side heat exchanger c106 and/or working-fluidbody c108, such as an upper radial portion (as shown) and/or a lowerradial portion. The second heat shield c127B may follow a contour orprofile of the hot-side heat exchanger c106 and/or working-fluid bodyc108. The second heat shield c127C may be disposed between the hot-sideheat exchanger c106 and a recirculation eductor c116.

In addition, or in the alternative, to the first heat shield c127A andthe second heat shield C127B, a heater body c100 may include a thirdheat shield c127C disposed about at least a portion of a combustor bodyc400. For example, the third heat shield c127 may circumferentiallysurround at least a portion of the combustion chamber c102, such as aproximal portion c200 of the combustion chamber c102.

It will be appreciated that the locations of the heat shields c127 shownin FIG. 4.1.7 are provided by way of example and are not to be limiting.In fact, a heat shield c127 may be provided at any desirable location ofa heater body c100. Other exemplary location for a heat shield c127 mayinclude an exhaust body c504, a heat recuperation body c500, a motiveannulus body c506, a conditioning conduit body c404, an eductor bodyc300, a regenerator body c800, a piston body c700, and/or arecirculation annulus body c302.

As discussed with reference to FIG. 4.1.3B, a heat shield may include acooling jacket c128 through which air may flow, such as from an intakeair annulus c216. Additionally, or in the alternative, in someembodiments a heat shield c127 may include an insulating material c129,such as shown in FIGS. 4.1.8A-4.1.8G. In an exemplary embodiment, theinsulating material c129 may be formed of an additive manufacturingmaterial, such as the same material as, or a different material fromthat, used to additively manufacture the heater body c100 or themonolithic body-segments that includes the insulating material c129.During operation of exemplary heater bodies c100, radiative heat mayrepresent a significant source of heat transfer. An insulating materialc129 may reduce the view factor of the heat shield c127, for example, ascompared to an air gap between an inner wall c130 and an outer wallc132. However, in some embodiments, a heat shield c127 may include aninsulating material c129 and an air jacket c128, which may also providean improved view factor. For example, as shown in FIG. 4.1.7, the firstheat shield c127A may include an insulating material c129 and an airjacket c128. Exemplary insulating materials c129 provide a view factorof zero as between opposite portions of the heater body c100, such asbetween an inner wall c130 and an outer wall c132.

In some embodiments, as shown in FIGS. 4.1.8A, and 4.1.8C-4.1.8G, aninsulating material c129 of a heat shield c127 may include aradiative-heat shield c129A. The radiative-heat shield c129A may includeany additively printed structure configured to shield the outer wallc132 from radiative heat from the inner wall c130, or vice versa. Insome embodiments, as shown for example in FIG. 4.1.8A, three-dimensionalunit cells, such as a three-dimensional array of unit cells. Such unitcells may have any desired shape, including polyhedral unit cells,conical unit cells, spherical unit cells, and/or cylindrical unit cells.The unit cells in a radiative-heat shield c129 may include open cellsand/or closed cells. As shown in FIGS. 4.1.8D-4.1.8G, the radiant heatshield may include elongate shield elements that are formed assubstantially independent additive structures, such as slanted elongateadditive structures (FIG. 4.1.8D), horizontal elongate additivestructures (FIG. 4.1.8E), and/or vertical additive structures (FIGS.4.1.8F and 4.1.8G). As shown, a radiative-heat shield C129A may includeone or more elongate shield elements, including less than five (5)elongate shield elements (FIGS. 4.1.8F) and/or less than two (2)elongate shield elements (FIG. 4.1.8G).

The radiative-heat shield c129A may be disposed within any portion of aheater body c100, such as between an inner wall c130 and an outer wallc132. The radiative-heat shield c129A may be an additively manufacturedstructure, which may be formed as part of the additive manufacturingprocess used to form a heater body c100 or a monolithic body-segmentthat defines a portion of the heater body c100. The radiative-heatshield c129A may be integrally formed with adjacent material of theheater body c100. In an exemplary embodiment, the radiative-heat shieldc129 may provide a view factor of zero as between opposite portions ofthe heater body c100, such as between an inner wall c130 and an outerwall c132.

In some embodiments, the radiative-heat shield c129A may have across-sectional thickness of about 100 micrometers to about 5,000micrometers, such as from about 750 micrometers to about 2,000micrometers, such as from about 1,000 micrometers to about 1,500micrometers. In some embodiments, the radiative-heat shield c129A mayinclude unit cells with walls that have a thickness of from about 50micrometers to about 500 micrometers, such as from about to about 125micrometers to about 250 micrometers.

Heat conduction posts c131 may monolithically connect the radiative-heatshield c129A with an adjacent portion of the heater body c100, such aswith an inner wall c130 and an outer wall c132 as shown. The conductionposts c131 may additionally or alternatively provide separation betweenthe radiative-heat shield and adjacent portions of the heater body c100.The dimensions and/or quantity of the heat conduction posts c131 may beselected at least in part to augment a rate of conductive heat transferbetween the radiative-heat shield c129A and an adjacent body c100. Forexample, relatively small, infrequently spaced, conduction posts c131may be positioned on a hot-side of the radiative-heat shield c129A.Additionally, or in the alternative, relatively large, regularly spaced,conduction posts c131 may be positioned at least in part to conductivelytransport heat from the radiative-heat shield c129A to a desired portionof the heater body c100. For example, such conduction posts c131 may beconfigured and arranged so as to transport heat from a radiative-heatshield c129A to a recirculation eductor c116, where the heat may beadvantageously utilized to preheat intake air and/or reheat combustiongas circulating through the recirculation pathway c104.

In some embodiments, as shown in FIG. 4.1.8B, an insulating materialc129 may include a powder material c129B, such as an additivemanufacturing powder material. The powder material c129B may be the sameas that utilized to additively manufacture the heater body c100 and/or amonolithic body-segment thereof. The powder material c129B may beunsintered or partially sintered. The powder material c129B may exhibita lower thermal conductivity relative to solidified material of theheater body c100. In some embodiments, as shown in FIG. 4.1.8C, aninsulating material c129 may include a combined powder-radiative-heatshield c129C made up of a radiative-heat shield (e.g., athree-dimensional array of unit cells) c129A and a powder material (anadditive manufacturing powder material) c129B disposed interstitiallyabout the radiative-heat shield c129A. In some embodiments, closed cellsof the radiative-heat shield c129 may include a powder material c129B,defining a powder-radiative-heat shield c129C. Additionally, or in thealternative, open cells of a radiative-heat shield c129A may includepowder material c129B, defining a powder-radiative-heat shield c129C.

The powder-radiative-heat shield c129 may be configured and arranged atleast in part to augment a rate of heat transfer between thepowder-radiative-heat shield c129C and an adjacent body c100. Forexample, closed cells may be utilized to provide a conductive heattransfer modality, and/or open cells may be utilized to provide aradiative heat transfer modality. The powder-radiative-heat shield c129Cmay be configured and arranged at least in part to transport heat fromthe powder-radiative-heat shield c129C to a desired portion of theheater body c100. For example, a powder-radiative-heat shield c129C maybe configured and arranged so as to transport heat from a hot-side heatexchanger c106 to a working-fluid body c108, or vice versa.Additionally, or in the alternative, a powder-radiative-heat shieldc129C may be configured and arranged so as to transport heat from ahot-side heat exchanger c106 and/or a working-fluid body c108 to arecirculation eductor c116, where the heat may be advantageouslyutilized to preheat intake air and/or reheat combustion gas circulatingthrough the recirculation pathway c104.

Referring now to FIGS. 4.1.7 and 4.1.9, in some embodiments, an heaterbody c100 may include one or more heat-capture pathways c133. The one ormore heat-capture pathways c133 may be defined by the monolithicstructure of the heater body c100 and/or by the monolithic structure ofone or more monolithic body segments that make up the heater body c100.A heat-capture pathway c133 may be provided at any desired location ofthe heater body c100. The heat-capture pathway c133 may be configured totransport a heat-capture fluid. As used herein, the term “heat-capturefluid” includes any suitable fluid transported through a heat-capturepathway c133 that, during operation of the heater body c100, has atemperature that is lower than a portion of the heater body c100intended to be cooled by the fluid in the heat-capture pathway c133.

A heat-capture pathway c133 may capture heat from one or more regions ofa heater body c100. In some embodiments, a heat-capture pathway c133 mayinclude a flowpath configured to flow a fluid disposed within theheat-capture pathway c133 to a relatively hotter region of the heaterbody c100, such as from a radially or concentrically outward portion ofthe heater body c100 to a radially or concentrically inward portion ofthe heater body c100, and/or from a distal portion of the heater bodyc100 to a proximal portion of the heater body c100. By way of example, aheat-capture pathway c133 may include a flowpath configured to flow afluid to the combustion chamber c102 and/or an upstream portion of ahot-side heater body c106. Additionally, or in the alternative, aheat-capture pathway c133 may cool hot portions of the heater body c100,for example to maintain suitable operating temperatures and/or to shieldusers or surrounding equipment from hot portions of the heater bodyc100.

In an exemplary embodiment, the heat-capture fluid may include a processfluid derived from a fluid pathway located elsewhere in the heater bodyc100, such as a fluid extracted from a primary flowpath c121 of theheater body c100. For example, the heat-capture fluid may include aprocess gas, such as intake air, exhaust gas, combustion gas, and/or afuel. Such combustion gas may include a combination of intake air, fuel,uncombusted or partially combusted combustion gas c428, and/or exhaustgas. Intake air may be supplied from an intake air pathway c118 to aheat-capture pathway c133 fluidly communicating with the intake airpathway c118. Exhaust gas may be supplied from an exhaust pathway c120to a heat-capture pathway c133 fluidly communicating with the exhaustpathway c120. Combustion gas may be supplied from a recirculationpathway c104 to a heat-capture pathway c133 fluidly communicating withthe recirculation pathway c104. Fuel may be supplied from a fuel supplyline to a heat-capture pathway c133 fluidly communicating with the fuelsupply line.

In some embodiments, the heat-capture pathway c133 may be configured todischarge a cooling fluid to a fluid pathway located elsewhere in theheater body c100 after having been utilized to provide cooling to alocation of the heater body c100. For example, a heat-capture pathwayc133 may be configured to discharge a cooling fluid to a location alonga primary flowpath c121 of the heater body c100, such as to an intakeair pathway c118, an exhaust gas pathway c120, a recirculation pathwayc104, and/or a fuel line c103. The heat-capture pathway c133 maydischarge cooling fluid to a fluid pathway of the primary flowpath c121that is the same or different from the fluid pathway of the primaryflowpath c121 from which the cooling fluid is obtained. For example, aheat-capture pathway c133 that utilizes intake air for cooling maydischarge to an intake air pathway c118. Additionally, or in thealternative, a heat-capture pathway c133 that utilizes intake air forcooling may discharge to an exhaust gas pathway c120, to a recirculationpathway c104, and/or to a fuel line c103. A heat-capture pathway c133that utilizes combustion gas, fuel, and/or exhaust gas, may discharge toan intake air pathway c118, an exhaust gas pathway c120, a recirculationpathway c104, and/or a fuel line c103. In some embodiments, aheat-capture pathway c133 may include a cooling jacket c128.Additionally, or in the alternative, a heat-capture pathway c133 mayfluidly communicate with a cooling jacket c128.

As used herein, the term “heat-capture pathway” includes any fluidpathway configured to capture heat from a location of the heater bodyc100, and/or to provide cooling to a location of the heater body c100,apart from heat transfer that occurs along the primary flowpath c121. Aheat-capture pathway c133 that utilizes a fluid from the primaryflowpath c121 may be differentiated from the primary flowpath c121 bythe heat-capture pathway c133 having an intended purpose of capturingheat from one or more portions of the heater body c100, and/or providingcooling to one or more portions of the heater body c100, separate andapart from a respective intended purpose of the primary flowpath c121,even though portions of the primary flowpath c121 inherently provideheat capture and/or cooling with respect to portions of the heater bodyc100. By way of example, a heat-capture pathway c133 that utilizes fluidfrom the primary flowpath c121 may transects a portion of the heaterbody c100 that differs from that of the primary flowpath c121, therebycapturing heat from a portion of the heater body c100 located elsewhererelative to the primary flowpath c121 and/or providing cooling to aportion of the heater body c100 located elsewhere relative to theprimary flowpath c121. Additionally, or in the alternative, aheat-capture pathway c133 that utilizes fluid from the primary flowpathc121 may have an inlet and an outlet that fluidly communicate withrespectively different portions of the primary flowpath c121. Aheat-capture pathway c133 that utilizes fluid from the primary flowpathc121 may additionally or alternatively have a heat transfer relationshipwith a location of the heater body c100 where, during operation of theheater body c100, at least one location of the heater body c100 has aheat transfer relationship with respect to the fluid in the heat-capturepathway c133 that includes a temperature gradient that is greater thanthe temperature gradient of a heat transfer relationship between suchlocation of the heater body c100 and the primary flowpath c121. By wayof contrasting illustration, the respective flowpaths of therecirculation eductor c116 and/or of the heat recuperator c124 flow totheir respective locations along the recirculation pathway c104 or theexhaust gas pathway c120, and are thereby differentiated from aheat-capture pathway c133.

In some embodiments, a heat-capture pathway c133 may utilize a coolingfluid that remains fluidly separate from the primary flowpath c131. Forexample, a heat-capture pathway c133 may utilize a chiller working fluid(e.g., a refrigerant), such as from a chiller assembly A40, as describedherein. Additionally, or in the alternative, a heat-capture pathway c133may utilize an engine-working fluid, such as from a working-fluidpathway c110, as described herein.

FIGS. 4.1.7 and 4.1.9 show an exemplary heat-capture pathway c133. Asshown, a heat-capture pathway c133 may provide cooling to an interfacebetween a heater body c100 and another portion an engine assembly 900.The heat-capture pathway c133 may provide cooling to a portion of theheater body c100 that includes a working-fluid body c108, a piston bodyc700, and/or a regenerator body c800. The heat-capture pathway c133 mayadditionally or alternatively provide cooling to a portion of the heaterbody c100 that interfaces with a working-fluid body c108, a piston bodyc700, and/or a regenerator body c800. The heat-capture pathway c133 mayalso return heat to the heater body c100, such as to an interior heaterbody-portion c100A of the heater body, such as a combustor body c400. Asshown, the heat-capture pathway c133 may provide cooling to an interfacebetween the heater body c100 and an engine body c050. In someembodiments, the heat-capture pathway c133 may provide cooling to aportion of the heater body c100 that interfaces with the engine bodyc050, such as to a working-fluid body c108, a piston body c700, and/or aregenerator body c800. As shown in FIG. 4.1.7, the heat-capture pathwayc133 may fluidly communicate with an intake pathway c118, and mayutilize intake air from the intake air pathway c118. Additionally, or inthe alternative, the heat-capture pathway c133 may fluidly communicatewith a cooling jacket c128 and may utilize a fluid such as intake airfrom the cooling jacket c128.

As shown in FIG. 4.1.9, a heat-capture pathway c133 maycircumferentially surround at least a portion of a piston chamber c112.A first heat-capture pathway-portion c133A of the heat-capture pathwayc133 may flow circumferentially around a first semiannular pistonchamber-portion c112A of the piston chamber c112. A second heat-capturepathway-portion c133B may flow circumferentially around a secondsemiannular piston chamber-portion c112B. The first heat-capturepathway-portion c133A and the second heat-capture pathway-portion c133Bmay reunite and/or fluidly communicate at an inward perimeter pistonchamber-portion c112C of the piston chamber c112. As shown, the firstheat-capture pathway-portion c133A and the second heat-capturepathway-portion c133B first heat-capture pathway-portion c133A and thesecond heat-capture pathway-portion c133B reunite, without fluidlycommunicating, at the inward perimeter piston chamber-portion c112C. Insome embodiments, the heat-capture pathway c133 (e.g., the firstheat-capture pathway-portion c133A and/or the second heat-capturepathway-portion c133A) may have a heat transfer relationship with athermal expansion joint c135. For example, as shown, the heat-capturepathway c133 may include a hairpin c133D that follows a perimeter of thethermal expansion joint c135.

In some embodiments, a fluid flowing through the heat-capture pathwayc133 may fluidly communicate with the primary flowpath c121, and fluidflowing through the heat-capture pathway c133 may be discharged from theheat-capture pathway c133 to the primary flowpath c121. As shown, theheat-capture pathway c133 may fluidly communicate with the recirculationpathway c104, such as at the combustion chamber c104. In someembodiments, fluid in the heat-capture pathway c133 may discharge intothe combustion chamber c104 through a distal portion of the combustionchamber c102. The distal portion of the combustion chamber c104 mayinclude a plurality of openings providing fluid communication with theheat-capture pathway c133. The plurality of openings may include aplurality of pore-like openings c137A (FIG. 4.5.5D) circumferentiallysurrounding the vortex conditioner c137 and/or disposed about the vortexconditioner c137. The heat-capture pathway c133 may transect at leastsome of the distal portion of the combustion chamber C102A, therebyproviding cooling to the combustion chamber c102. In some embodiments,the heat-capture pathway c133 may include a plurality ofspiral-heat-capture pathways c133E disposed about the distal portion ofthe combustion chamber C102A (FIG. 4.5.5D). In some embodiments,heat-capture fluid in the heat-capture pathway c133 may have a heattransfer relationship with a portion a heater body c100 that would becapable of exceeding a threshold temperature during operations, such asa threshold temperature determined in relation to a melting temperature,whereas the heat-capture fluid operates to maintain such portion of theheater body c100 below such threshold temperature during operations.

Now referring to FIG. 4.1.10, in some embodiments, an interface betweena heater body c100 and an engine body c050 may include anengine-to-heater coupling c137. In some embodiments, theengine-to-heater coupling c139 may include a fitting c141, such as atri-clamp fitting or any other suitable fitting, configured to couple aheater body-flange c143 and an engine body-flange c145 to one another. Agasket c147 may be disposed between the heater body-flange c143 and theengine body-flange c145. A heat-capture pathway c133 may capture heatfrom a region of the heater body c100 that includes the heaterbody-flange c143, and/or provide cooling to a region of the heater bodyc100 that includes the heater body-flange c143. Heat captured from suchregion of the heater body c100 may be returned to another portion of theheater body, thereby preventing the heat from being lost to the enginebody c050, which may include a cold-side of a closed-cycle engine. Whilethe embodiment shown in FIG. 4.1.10 depicts a fitting c141, other typesof fittings are also contemplated. A fitting c141 may allow for thermalexpansion as a result of heat from the heater body c100, as well asdifferences in temperature as between the heater body c100 and theengine body c050.

In some embodiments, an engine-to-heater coupling c137 may include agasket c147 formed at least in part from a polymeric material, such assilicone, fluorosilicone, fluorocarbon, nitrile rubber,polytetrafluoroethylene (PTFE), ethylene propylene diene monomer rubber(EPDM), polyamides, aramid fiber-polymeric laminates, carbonfiber-polymeric laminates, graphite-polymeric laminates, or the like.Such gaskets formed of a polymeric material may advantageously have arelatively low thermal conductivity, which may reduce heat loss from theheater body c100 to the engine body c050. Additionally, or in thealternative, an engine-to-heater coupling c137 may utilize a gasket c147that includes of a non-polymeric material, such as a ceramic or metallicmaterial. For example, a gasket c147 may include metal alloys, ceramics,vermiculite, woven or compressed graphite, ceramic fiber, fiberglass, orthe like.

In some embodiments, cooling provided by a heat-capture pathway c133 mayallow for temperatures existing at the interface between the heater bodyc100 and the engine body c050 to remain within a range suitable forusing a gasket c147 formed at least in part of a polymeric material. Insome embodiments, at least a portion of the heater body c100 may exceeda maximum operating temperature of a gasket c147 while a region of theheater body c100 that includes the heater body-flange c143 may be withinthe maximum operating temperature of the gasket c147. The region of theheater body c100 that includes the heater body-flange c143 may bemaintained below the maximum operating temperature of the gasket c147 atleast in part by cooling provided by the heat-capture pathway c133. Insome embodiments, such polymeric materials would be unsuitable for useat the engine-to-heater coupling c137, if not for the cooling providedby the heat-capture pathway c133, at least in part due to thetemperature of the heater body c100 otherwise exceeding the maximumoperating temperature of the gasket c147. Such maximum operatingtemperature may be specified by a manufacturer of the gasket and/or byan industry standards organization such as ASTM. Such polymericmaterials may also provide for a degree of flexibility and vibrationabsorption at the interface between the heater body c100 and the enginebody c050.

By way of example, in some embodiments at least a portion of a heaterbody c100 may exhibit an operating temperature in excess of about 400 C,such as at least about 500 C, such as at least about 600 C, such as atleast about 700 C, or such as at least about 800 C. Meanwhile, while atleast a portion of the heater body exhibits an aforementioned operatingtemperature, in some embodiments, a region of the heater body c100 thatincludes the heater body-flange c143 may exhibit an operatingtemperature of at least less than 600 C, such as at least less than 500C, such as at least less than 400 C, such as at least less than 300 C,or such as at least less than 200 C.

In some embodiments a region of the heater body c100 that includes theheater body-flange c143 may exhibit an operating temperature of at leastabout 50 C cooler than another region of the heater body c100, such asthe working-fluid body c108. For example, the region of the heater bodyc100 that includes the heater body-flange c143 may be at least about 50C cooler than a portion of the heater body c100 that includes theworking-fluid body c108, such as at least about 75 C cooler, such as atleast about 100 C cooler, such as at least about 200 C cooler, such asat least about 300 C cooler, or such as at least about 400 C cooler,than such region of the heater body c100 that includes the working-fluidbody c108. Such temperature difference in operating temperature may beattributable at least in part to cooling provided by a cooling fluid ina heat-capture pathway c133.

Now referring to FIGS. 4.2.1A and 4.2.1B, and 4.2.2A and 4.2.2B,exemplary combustor bodies c400 will be described. The presentlydisclosed combustor bodies c400 may define part of a heater body c100and/or a closed-cycle engine c002. For example, a combustor body c400may define at least a portion of a monolithic body or a monolithicbody-segment. Such monolithic body or monolithic body-segment may defineat least a portion of the heater body c100 and/or the closed-cycleengine c002. Additionally, or in the alternative, the presentlydisclosed combustor bodies c400 may be provided as a separate component,whether for use in connection with a heater body c100, a closed-cycleengine c002, or any other setting whether related or unrelated to aheater body c100 or a closed-cycle engine c002. At least a portion ofthe combustor body c400 may define a combustion chamber c102 and/or aconditioning conduit c122. While the heater bodies c100 depicted in thefigures may show one combustor body c400 and/or one combustion chamberc102 and/or one conditioning conduit c122, it will be appreciated that aheater body c100 may include a plurality of combustor bodies c400 and/ora plurality of combustion chambers c102 and/or a plurality ofconditioning conduits c122. For example, a heater body c100 may includeone or more combustor bodies c400, and/or a combustor body c400 mayinclude one or more combustion chambers c102 and/or one or moreconditioning conduits c122. Exemplary heater bodies c100 and/orcombustor bodies c400 may be configured for single-stage combustionand/or multi-stage combustion. A heater body c100 and/or a combustorbody c400 configured for multi-stage combustion may include two, three,four, or more combustion zones.

As shown, an exemplary combustor body c400 may include a combustionchamber c102 and a conditioning conduit c122 circumferentiallysurrounding at least a portion of the combustion chamber c102. Thecombustion chamber c102 may be disposed annularly about an axis c204, orthe combustion chamber may be off-center from the axis c204. In someembodiments, a plurality of combustion chambers c102 may becircumferentially spaced about the axis c204. The combustion chamberc102 may include an annular combustion chamber wall c406. An inwardportion of the annular combustion chamber wall c406 may define at leasta portion of the combustion chamber c102. The conditioning conduit c122may include an outward annular conditioning conduit wall c408circumferentially surrounding the combustion chamber c122, and an inwardannular conditioning conduit wall c410 circumferentially surrounding theoutward annular conditioning conduit wall c408. An outward portion ofthe annular combustion chamber wall c406 may define at least a portionof the inward annular conditioning conduit wall c410. The inward portionof the annular combustion chamber wall c406 and the outward portion ofthe annular combustion chamber wall c406 may adjoin one another at adistal end c202 of the combustion chamber c102.

The combustion chamber c102 may include a combustion chamber outlet c412disposed about a proximal portion c202 of the combustion chamber c102.For example, the combustion chamber outlet c412 may be disposed about aproximal portion of an annular combustion chamber wall c406. Acombustion chamber c102 may include a single combustion chamber outletc412 or a plurality of combustion chamber outlets c412, and thecombustion chamber outlet or outlets c412 may be oblique to thecombustion chamber c102. For example, a plurality of combustion chamberoutlets c412 may be circumferentially spaced about a proximal portionc202 of the combustion chamber c102, such as about a proximal portionc202 of the annular combustion chamber wall c406.

The conditioning conduit c122 may fluidly communicate with thecombustion chamber c102 at a distal portion of the combustion chamberc102. The conditioning conduit c122 may include a conditioning conduitinlet c414 disposed about a proximal portion c202 of the conditioningconduit c122. For example, the conditioning conduit inlet c414 may bedisposed about a proximal portion of the outward annular conditioningconduit wall c408. A conditioning conduit c122 may include a singleconditioning conduit inlet c414 or a plurality of conditioning conduitinlets c414, and the conditioning conduit inlet or inlets c414 may beoblique to the conditioning conduit c120. For example, a plurality ofconditioning conduit inlets c414 may be circumferentially spaced about aproximal portion c202 of the conditioning conduit c122, such as about aproximal portion c202 of the outward annular conditioning conduit wallc408.

The inward annular conditioning conduit wall c410 may be defined atleast in part by the annular combustion chamber wall c406. In someembodiments, a portion of the inward annular conditioning conduit wallc410 may be separated from the annular combustion chamber wall c406,such that the inward annular conditioning conduit wall c410 and theannular combustion chamber wall c406 define an insulating spacetherebetween (not shown). For example, a medial portion of the inwardannular conditioning conduit wall c410 may be separated from the annularcombustion chamber wall c406 so as to define such an insulating space.

As shown in FIGS. 4.2.1A and 4.2.1B, the conditioning conduit c122 maydefine at least a portion of the recirculation pathway c104. The portionof the recirculation pathway c104 defined by the conditioning conduitc122 may sometimes be referred to as a conditioning conduit pathwayc416. The conditioning conduit pathway c416 may be defined at least inpart by the inward annular conditioning conduit wall c410 and theoutward annular conditioning conduit wall c408.

In exemplary embodiments, the one or more conditioning conduit inletsc414 may be disposed about a proximal portion c200 of the conditioningconduit c122 and oriented oblique to the conditioning conduit c122. Forexample, the one or more conditioning conduit inlets c414 may be obliqueto the outward annular conditioning conduit wall c408 and/or the inwardannular conditioning conduit wall c410. The one or more conditioningconduit inlets c414 may respectively include a motive pathway c418 andan eduction pathway c420 fluidly communicating with the conditioningconduit c122. As shown in FIGS. 4.2.1A and 4.2.1B, a plurality ofconditioning conduit inlets c412 may include a plurality of motivepathways c418 and a plurality of eduction pathways c420circumferentially spaced about the conditioning conduit c122.

The motive pathway c418 (or plurality of motive pathways c418) and theeduction pathway c420 (or plurality of eduction pathway c420) may bedefined at least in part by an eductor body c300. The motive pathwayc418 or plurality of motive pathways define a portion of an intake airpathway and the eduction pathway or plurality of eduction pathwaysdefine a portion of a recirculation pathway. The eduction pathway c420and the motive pathway c418 may be adjacent to one another, such thatintake air flowing through the motive pathway c418 may accelerate andentrain combustion gas from the eduction pathway c420 so as to movecirculating combustion gas into the conditioning conduit c122. Themotive pathway c418 and the eduction pathway c420 are preferablyoriented oblique to the conditioning conduit c122 (e.g., oblique to theoutward annular conditioning conduit wall c408 and/or the inward annularconditioning conduit wall c410), such that intake air and combustion gasflowing into the conditioning conduit may readily establish a helicalflow pattern through the conditioning conduit c122.

In exemplary embodiments, the one or more combustion chamber outletsc412 may be disposed about a proximal portion c200 of the combustionchamber c102 and oriented oblique to the combustion chamber c102. Forexample, the one or more combustion chamber outlets c412 may be obliqueto the annular combustion chamber wall c406. The one or more combustionchamber outlets c412 may fluidly communicate with a correspondingplurality of combustion-gas pathways c422 circumferentially spaced aboutthe combustion chamber c102. The plurality of combustion-gas pathwaysc422 may fluidly communicate with a respective portion of the combustionchamber c102. Respective combustion-gas pathways c422 may extend in aradial, circumferential, and/or tangential direction relative to thecombustion chamber c102. For example, the respective combustion-gaspathways c422 may concentrically spiral radially or circumferentiallyoutward from the combustion chamber. The respective combustion-gaspathways c422 may extend annularly or semi-annularly along a spiral orspiral arc relative to the combustion chamber and/or the longitudinalaxis c204 thereof. As shown in FIGS. 4.2.1A and 4.2.1B, the plurality ofcombustion-gas pathways c422 define at least a portion of a hot-sideheat exchanger body c600. The oblique orientation of the one or moreconditioning conduit inlets c414 and/or of the one or more combustionchamber outlets c412 may cause combustion gas to swirl through theconditioning conduit c122, for example, from a proximal portion of theconditioning conduit c122 to a distal portion of the conditioningconduit c122 and through the combustion chamber c102 from a distalportion of the combustion chamber c102 to a proximal portion of thecombustion chamber 102.

The swirling combustion gas may provide a bidirectional coaxial vortexflow field. When the combustor body c400 includes a conditioning conduitc122, the conditioning conduit c122 provides separation between anoutward portion of the bidirectional coaxial vortex flow field and aninward portion of the bidirectional coaxial vortex flow field, theconditioning conduit defining a pathway for the outward portion of thebidirectional coaxial vortex flow field and the combustion chamberdefining a pathway for the inward portion of the bidirectional coaxialvortex flow field. Such separation of the bidirectional coaxial vortexflow field provided by the conditioning conduit c122 may enhancecombustion dynamics, for example, by reducing shear between the outwardand inward portions of the bidirectional coaxial vortex flow field.

In some embodiments, the annular combustion chamber wall c406 may have aCoanda surface c424 disposed at a distal end thereof defining atransition between an inner annular portion and an outer annular portionof the annular combustion chamber wall c406. The Coanda surface c424 maybe operable at least in part to draw combustion gas from theconditioning conduit c122 into the combustion chamber c102. A “Coandasurface” refers to a curved surface that creates a zone of reducedpressure in the immediate proximity of such curved surface. Thispressure drop entrains and accelerates fluid along the contour of thesurface, which is sometimes referred to as the “Coanda effect.” TheCoanda effect is the phenomena in which a flow attaches itself to anearby surface and remains attached even though the surface curves awayfrom the initial direction of flow. Characteristic of the Coanda effect,fluid tends to flow over the surface closely, seemingly “clinging to” or“hugging” the surface. As such, the Coanda effect can be used to changethe direction of the combustion gas swirling through the conditioningconduit c122 and into the combustion chamber c122. In doing so, acombustion flame c426 may be surrounded by a flow of cooler, uncombustedor partially combusted combustion gas c428, thereby form a boundarylayer separating the flame c426 from the annular combustion chamber wallc406.

In some embodiments, the combustor body c400 may include a combustor capc210 disposed axially adjacent to a distal portion of the conditioningconduit c122. The combustor cap c210 may be operably coupled to thecombustor body c400, for example, using bolts (not shown) insertableinto bolt holes c430. Alternatively, the combustor cap c210 may define aportion of a monolithic body or a monolithic body-segment that includesat least a portion of the combustor body c400. As yet anotheralternative, the combustor cap c210 may be integrally formed with atleast a portion of the combustor body c400. In an exemplary embodiment,the combustor cap c210 may be operably coupled to the conditioningconduit body c404, or the combustor cap c210 may define a portion of theconditioning conduit body c404 or may be integrally formed with theconditioning conduit body c404.

As shown in FIGS. 4.2.1A and 4.2.1B, the combustor cap c210 includes aninward combustor cap wall c432 defining a portion of the recirculationpathway c104. The portion of the recirculating pathway c104 includingthe inward combustor cap wall c432 may provide fluid communicationbetween the conditioning conduit c122 and the combustion chamber c102 ata distal portion of the combustion chamber c102, and the combustor capc210 may be operable at least in part to direct combustion gas from theconditioning conduit c122 to the combustion chamber c102. The combustorcap c210 may be disposed axially adjacent to a distal portion c202 ofthe conditioning conduit c122 and/or the combustion chamber c102.

The combustion chamber c102 and the conditioning conduit c122 may haveany desired shape. In various embodiments, the combustion chamber c102may have a shape including a cylinder and/or a frustum, and theconditioning conduit c122 may have a shape including a cylinder and/or afrustum. As shown in FIGS. 4.2.1A and 4.2.1B, the combustion chamberc102 and the conditioning conduit c122 respectively have a cylindricalshape. In other embodiments, a portion of the combustion chamber c102having a cylinder shape may be circumferentially surrounded by a portionof the conditioning conduit c122 having a cylinder shape and/or aportion of the conditioning conduit c122 having a frustum shape.Additionally, or in the alternative, a portion of the combustion chamberc102 having a frustum shape may be circumferentially surrounded by aportion of the conditioning conduit c122 having a cylinder shape and/ora portion of the conditioning conduit c122 having a frustum shape. Sucha frustum shape of the combustion chamber c102 and/or of theconditioning conduit c122 may converge proximally and/or divergeproximally.

By way of example, a first portion of a combustion chamber c102 may havea first shape that includes a cylinder, and the first portion of thecombustion chamber c102 may be circumferentially surrounded by a secondportion of the conditioning conduit c122 having a second shape thatincludes a cylinder and/or a frustum. Additionally, or in thealternative, a third portion of the combustion chamber c102 may have athird shape that includes a cylinder and/or a frustum, and the thirdportion of the combustion chamber c102 may be circumferentiallysurrounded by a fourth portion of the conditioning conduit c122 having afourth shape that includes a cylinder. Further in addition or in thealternative, a fifth portion of the combustion chamber c102 may have afifth shape that includes a frustum diverging proximally, and the fifthportion of the combustion chamber c102 may be circumferentiallysurrounded by a sixth portion of the conditioning conduit c122 having asixth shape that includes a frustum converging proximally and/or afrustum diverging proximally. Still further in addition or in thealternative, a seventh portion of the combustion chamber c102 may have aseventh shape that includes a frustum diverging proximally, and theseventh portion of the combustion chamber c102 may be circumferentiallysurrounded by an eighth portion of the conditioning conduit having aneighth shape that includes a frustum converging proximally and/or afrustum diverging proximally.

Referring now to FIG. 4.2.1B, in some embodiments, a combustor body c400may include one or more aerodynamic features c434. The one or moreaerodynamic features c434 may be disposed about at least a portion ofthe combustion chamber c102 and/or at least a portion of theconditioning conduit c122, such as the annular combustion chamber wallc406 (e.g. an inward surface and/or an outward surface thereof), theoutward annular conditioning conduit wall c408, and/or the inwardannular conditioning conduit wall c410. The one or more aerodynamicfeatures c434 may be configured to condition the flow of combustion gasc428 flowing through the conditioning conduit c122, such as by swirlingthe flow of combustion gas c428. Additionally, or in the alternative,the one or more aerodynamic features c434 may be configured to conditionthe flow of combustion gas c428 or the flame c426 flowing through thecombustion chamber c102, such as by swirling the flow of combustion gasc428 and/or flame c426. For example, the one or more aerodynamicfeatures c434 may include a fin, a ridge, a groove, a contour, and/orthe like disposed about the combustion chamber c102 and/or theconditioning conduit c122.

The one or more aerodynamic features c434 may followed a helicalorientation along the combustion chamber c102 and/or the conditioningconduit c122. The helical orientation of the one or more aerodynamicfeatures c434 may help condition the flow of combustion gas c428 and/orthe flame c426 in a helical path. For example, the combustion gas c428and/or the flame c426 may follow a helical path that depends at least inpart on the slope of the helical orientation of the one or moreaerodynamic features c434. Additionally, or in the alternative, suchhelical path of the combustion gas c428 and/or the flame c426 may dependon the size, number, and/or spacing of the one or more aerodynamicfeatures c434. In an exemplary embodiment, the one or more one or moreaerodynamic features c434 may provide a bidirectional coaxial vortexflow field, which may enhance heat transfer of the flame c426 to thehot-side heater body c106 and/or may protect the combustion chamber wallc406 from receiving excessive heat from the flame c426.

As shown in FIG. 4.2.1B, the one or more aerodynamic features c434 mayinclude a first helical conditioning ridge c436 be disposed about theannular combustion chamber wall c406 (e.g. an outward surface thereof).Additionally, or in the alternative, the one or more aerodynamicfeatures c434 may include a second helical conditioning ridge c438disposed about the inward annular conditioning conduit wall c410 and/ora third helical conditioning ridge c440 disposed about the outwardannular conditioning conduit wall c408.

Still referring to FIGS. 4.2.1A and 4.2.1B, the combustor body c400and/or the combustion chamber c102 may have an axial length selectedbased at least in part on a desired flame length and/or a correspondingcombustion time. In some embodiments, the combustion time may be from 1to 10 milliseconds, such as from 2 to 4 milliseconds. The combustiontime may be at least 1 millisecond, at least 2 milliseconds, or at least5 milliseconds. The combustion time may be less than 10 milliseconds,less than 7 milliseconds, or less than 3 milliseconds.

The flame c426 may have an axial length extending all or a portion ofthe combustion chamber c102. In some embodiments, the flame c426 mayextend though one or more combustion chamber outlets c412 and into thehot-side heat exchanger c106. The hot-side heat exchanger c106 mayinclude working-fluid pathways c110; however, in some embodiments, theworking-fluid pathways c110 may be omitted from a radially orconcentrically inward portion of the hot-side heat exchanger c106 so asto facilitate the flame c426 flowing into the hot-side heat exchangerc106. Such a radially-inward portion of the hot-side heat exchanger c106may define a combustion zone where combustion may occur in the hot-sideheat exchanger c106. The combustion that occurs in the hot-side heatexchanger may represent an extension of combustion that occurs in thecombustion chamber c102, such as in the case of a flame that extendsfrom the combustion chamber into the hot-side heat exchanger c106. Theradially-inward portion of the hot-side heat exchanger c106 mayadditionally/or alternatively support stable combustion separate anddistinct from the combustion that occurs in the combustion chamber c10.For example, a first flame c426 in the combustion chamber may quenchupstream from the hot-side heat exchanger c106, and a second flame c426may be established and stabilize in the radially-inward portion of thehot-side heat exchanger c106.

The radially-inward portion of the hot-side heat exchanger c106 maysometimes be referred to as a second combustion chamber c448, in whichcase, the combustion chamber c102 may be referred to as a firstcombustion chamber c102. In some embodiments, the flame c426 may extendinto the combustion chamber c448. Additionally, or alternatively, asecond flame c426 may exist in the second combustion chamber c448,defining a combustion zone that is separate from a combustion zone inthe second combustion chamber c448 may include a plurality of combustionfins c450 circumferentially spaced about the combustion chamber c102.The combustion fins c450 may occupy a region of the hot-side heatexchanger c106 configured for stable combustion to occur. Combustion mayoccur in the region of the hot-side heat exchanger c106 where thecombustion fins c450 are located at least in part by the combustion finsc450 being heated to a sufficiently high temperature during operation toprevent flame quenching and/or promote an extended flame length.

The plurality of combustion fins c450 may spiral concentrically relativeto the combustion chamber c102 and/or the longitudinal axis c204thereof. The plurality of combustion fins c450 may be configured andarranged as spirals or spiral arcs, disposed annularly orsemi-annularly, relative to the combustion chamber c102 and/or thelongitudinal axis c204 thereof. The combustion fins c450 may beconcentrically nested with one another. Concentrically nested combustionfins c450 may be configured as an array of substantially concentricspirals and/or an array of substantially concentric spiral arcs. By wayof example, a spiral or spiral arc, such as in an array of substantiallyconcentric spirals or spiral arcs, may correspond to at least a portionof an Archimedean spiral, a Cornu spiral, a Fermat's spiral, ahyperbolic spiral, a logarithmic spiral, a Fibonacchi spiral, aninvolute, or a squircular spiral, as well as combinations of these.

Upstream portions of the respective combustion-gas pathways c422 mayfluidly communicate with the combustion chamber c102 at respectivecircumferential locations about the perimeter of the combustion chamberc102. Downstream portion of the respective combustion-gas pathways c422may fluidly communicating with corresponding heating fluid pathways c602of the hot-side heat exchanger c106 (e.g. FIGS. 4.4.2A, 4.4.2B, 4.4.3A,and 4.4.3B). Such combustion fins c450 may concurrently define at leasta portion of the second combustion chamber c448 and at least a portionof the hot-side heat exchanger c106. The combustion fins c450 may becomered-hot, encouraging a sustained combustion flame within the secondcombustion chamber c448. The second combustion chamber c448 may allowcombustion to take place at an air-to-fuel ratio closer to thestoichiometric air-to-fuel ratio.

The combustor body c400 may include one or more features of thecombustion chamber c102 and/or one or more features of the conditioningconduit c122 configured to burn fuel in a lean combustion environment.For example, the conditioning conduit c122 may include one or moreconditioning conduit inlets c414 dimensionally configured to providesufficient combustion gas flow for a lean combustion environment.Additionally, or in the alternative, the one or more features of thecombustion chamber c102 may include one or more combustion chamberoutlets dimensionally configured to provide sufficient combustion gasflow for a lean combustion environment. The combustor body c400 mayinclude one or more fuel nozzles, and the one or more fuel nozzles maybe configured to provide a fuel flow sufficient for a lean combustionenvironment.

With respect to the one or more conditioning conduit inlets c414, thelean combustion environment may be provided by one or more motivepathways c418 and/or one or more eduction pathways c420. The one or moremotive pathways c418 may be dimensionally configured to supply theconditioning conduit c122 and/or the combustion chamber c102 withsufficient intake air to from the intake air pathway c118 to provide alean combustion environment. Additionally, or in the alternative, theone or more motive pathways c418 may be dimensionally configured toaccelerate and entrain sufficient combustion gas from the recirculationpathway c104 to provide a lean combustion environment. The one or moreeduction pathways c420 may be dimensionally configured to recirculatesufficient combustion gas from the recirculation pathway c104 to providea lean combustion environment.

A lean combustion environment may be characterized by an equivalenceratio, which is the ratio of the actual fuel-to-air ratio to thestoichiometric fuel-to-air ratio. An exemplary lean combustionenvironment may include an equivalence ratio of 0.6 to 1.0, such as anequivalence ratio of 0.7 to 0.8. The equivalence ratio may be at least0.6, such as at least 0.8. The equivalence ratio may be less than 1.0,such as less than 0.7. An exemplary lean combustion environment mayinclude an air-to-fuel ratio of from 40:1 to 90:1 by mass, or from 55:1to 75:1 by mass. The air-to-fuel ratio may be at least 40:1 by mass,such as at least 55:1 by mass. The air-to-fuel ratio may be less than90:1 by mass, such as less than 75:1 by mass.

The combustor body c400 may include one or more features of thecombustion chamber c102 and/or one or more features of the conditioningconduit c122 configured to circulate at least a portion of thecombustion gas by volume and to introduce a balance of the combustiongas as intake air. For example, the conditioning conduit c122 mayinclude one or more conditioning conduit inlets c414 dimensionallyconfigured to circulate at least a portion of the combustion gas byvolume and to introduce a balance of the combustion gas as intake air.Additionally, or in the alternative, the one or more features of thecombustion chamber c102 may include one or more combustion chamberoutlets dimensionally configured to circulate from at least a portionthe combustion gas by volume and to introduce a balance of thecombustion gas as intake air.

The volume of circulating combustion gas may be from about 10% to about90% of the combustion gas, such as from about 30% to about 70% of thecombustion gas, such as from about 40% to about 60% of the combustion,with the balance of the combustion gas as being intake air. The volumeof intake air included in the combustion gas may be from about 10% toabout 90% of the combustion gas, such as from about 30% to about 70% ofthe combustion gas, such as from about 40% to about 60% of thecombustion, with the balance being circulated combustion gas. However,in some embodiments the combustor body c400 may utilize 100% intake airand/or 100% circulating combustion gas.

In some embodiments, a cooling jacket c442 disposed within the at leasta portion of the combustor body c400. The cooling jacket may define apathway for a cooling fluid to flow within the combustor body c400. Theflow of fluid cooling fluid may provide cooling to the combustor bodyc400. The cooling jacket c442 may fluidly communicate with the intakeair pathway c118, the recirculation pathway c104, and/or theworking-fluid pathway c110. By way of example, as shown in FIG. 4.1.1A,a cooling jacket c442 may be disposed between at least a portion of theinward portion of the annular combustion chamber wall c406 and theoutward portion of the annular combustion chamber wall c406, with thecooling jacket c442 fluidly communicating with at least one of the oneor more motive pathways c418. Additionally, or in the alternative, thecooling jacket c442 shown in FIG. 4.1.1A may fluidly communicate with atleast one of the one or more eduction pathways c420. When the coolingfluid for the cooling jacket includes intake air and/or combustion gas,the combustor body c400 may include one or more cooling-jacket outletsc444, allowing the cooling fluid to flow into the conditioning conductc122 and/or the combustion chamber c102.

Referring again to FIG. 4.1.1B, in some embodiments, a combustor bodyc400 may include a plurality of conditioning pathways c446 traversingthe annular combustion chamber wall c406. The conditioning pathways maybe disposed about a proximal, medial, and/or axial portion of thecombustion chamber c102, for example, traversing a proximal, medial,and/or axial portion of the annular combustion chamber wall c406 andproviding fluid communication between the combustion chamber c102 andthe conditioning conduit c122.

Now referring to FIGS. 4.2.2A and 4.2.2B, an exemplary heater body c100and/or combustor body c400 configured for multi-stage combustion will bedescribed. A combustor body c400 configured for multi-stage combustionmay sometimes be referred to as a multi-stage combustor c403. As usedherein, the term “multi-stage combustion” refers to a combustion regimethat includes at least two combustion zones oriented in serial flowrelationship. As used herein, the term “combustion zone” refers to aportion of a combustion gas and/or fuel flowpath configured to support astable flame c426 under one or more operating conditions. In someembodiments, a combustion zone may include a fuel injection point. Forexample, a multi-stage combustor may include a plurality of fuelinjection points in serial flow relationship that are respectivelyconfigured to support a stable flame c426. Additionally, or in thealternative, a multi-stage combustor may include a combustion zone thatis configured to support a stable flame c426 by combusting a fuel and/orcombustion gas c428 introduced into the flowpath at an upstreamcombustion zone. For example, a fuel-rich environment may allow for areburn combustion regime in which fuel injected at a first combustionzone is partially combusted at the first combustion zone and thenfurther combusted at a second combustion zone.

An exemplary multi-stage combustor c403 may include a primary combustionzone and a secondary combustion zone. In some embodiments, a multi-stagecombustor may include a tertiary combustion zone. The primary combustionzone may be situated upstream and/or downstream from a secondarycombustion zone. A tertiary combustion zone may be located upstream ordownstream from a primary combustion zone, and/or upstream or downstreamfrom a secondary combustion zone. As used herein, the term “primarycombustion zone” refers to a combustion zone that generates a largerproportion of heat during steady-state operation relative to one or moreother combustion zones, such as relative to a secondary combustion zoneand/or relative to a secondary and tertiary combustion zone. As usedherein, the term “secondary combustion zone” refers to a combustion zonethat generates a lesser proportion of heat during steady-state operationrelative to another combustion zone, such as relative to a primarycombustion zone. The term “tertiary combustion zone” refers to acombustion zone that generates a lesser proportion of heat duringsteady-state operation relative to a plurality of other combustionzones, such as relative to a primary combustion zone and a secondarycombustion zone.

In an exemplary embodiment, a heater body c100 that includes amulti-stage combustor c403 may include a first combustion zone c405 anda second combustion zone c407. The first combustion zone c405 may occupya distal or medial position relative to the longitudinal axis c204 ofthe combustion chamber c102. The second combustion zone c407 may occupya proximal position relative to the longitudinal axis c204 of thecombustion chamber c102. The first combustion zone c405 may occupy aradially or concentrically inward position relative to the longitudinalaxis c204 of the combustion chamber c102. The second combustion zonec407 may occupy a radially or concentrically outward position relativeto the longitudinal axis c204 of the combustion chamber c102 and/orrelative to the radially or concentrically inward position of the firstcombustion zone c405. In some embodiments, the first combustion zonec405 may occupy at least a portion of a vortex flow field, such as abidirectional vortex flow field. For example, the first combustion zonec405 may occupy at least part of an inward portion of a bidirectionalcoaxial vortex flow field. The second combustion zone c407 may occupy atleast part of a proximal region of the combustion chamber c102.Additionally, or in the alternative, the second combustion zone c407 mayoccupy at least part of a radially-inward portion of the hot-side heatexchanger c106. For example, the hot-side heat exchanger c106 may definea second combustion chamber c448, and the second combustion zone c407may occupy at least a portion of the second combustion chamber c448.

The first combustion zone c405 may be located upstream from a heat sinkc409 a sufficient distance to allow combustion in the first combustionzone c405 to start, warm up, and stabilize. For example, the heat sinkc409 may include at least a portion of the working-fluid bodies c108and/or at least a portion of the hot-side heat exchanger c106. Theworking-fluid bodies c108 may have a heat transfer relationship with thehot-side heat exchanger c106. The heat sink c409 may include a pluralityof working-fluid pathways c110 that have a heat transfer relationshipwith the hot-side heat exchanger c108 and/or the plurality ofcombustion-gas pathways c422. The plurality of heating walls c616 maydefine at least a portion of the hot-side heat exchanger c106. Thehot-side heat exchanger c106 may include a plurality of working-fluidpathways monolithically formed within the plurality of heating wallsc616.

Combustion in the second combustion zone c407 may be initiatedconcurrently with and/or subsequently to initiation of combustion thefirst combustion zone c405. In some embodiments, combustion in thesecond combustion zone c407 may be initiated after combustion in thefirst combustion zone c405 has started, and/or after combustion in thefirst combustion zone c405 at least partially heated at least a portionof the combustor body c400 proximate to the second combustion zone c407.Additionally, or in the alternative, combustion in the second combustionzone c407 may be initiated after combustion in the first combustion zonec405 has stabilized.

Combustion in the first combustion zone c405 may be operated orsustained as a primary combustion zone. Additionally, or in thealternative, combustion in the first combustion zone c405 may beoperated or sustained as a secondary combustion zone, or even as atertiary combustion zone. In some embodiments, combustion in the firstcombustion zone c405 may be initially operated or sustained as a primarycombustion zone, such as during a warm-up period. After an initialoperating period, such as the warm-up period, combustion in the firstcombustion zone may transition to operation as a secondary combustionzone or a tertiary combustion zone. Combustion in the second combustionzone c407 may be operated or sustained as a primary combustion zoneand/or a secondary combustion zone. For example, combustion in thesecond combustion zone c407 may be operated or sustained as a primarycombustion zone after combustion in the first combustion zone c405 hassufficiently heated at least a portion of the combustor body c400proximate to the second combustion zone c407. As combustion in the firstcombustion zone c405 transitions to operation as a secondary combustionzone, combustion in the second combustion zone c407 may transition tooperation as a primary combustion zone. In some embodiments, combustionin the first combustion zone may be throttled back to a nominalproportion of combustion. For example, combustion in the firstcombustion zone c405 may operate at a nominal level sufficient tosustain steady combustion at the secondary combustion zone c407.

During operation, such as during steady state operation, combustion inthe first combustion zone c405 may support combustion in the secondcombustion zone c407 by maintaining a supply of heat sufficient tosustain at least a portion of the combustor body c400 proximate to thesecond combustion zone c407 at a temperature that exceeds a thresholdsuitable for good combustion and flame characteristics at the secondcombustion zone c407. Such support from the first combustion zone c405may advantageously allow the second combustion zone c407 to operate as aprimary combustion zone, thereby introducing heat closer to a heat sinksuch as a working-fluid body c108 and/or a hot-side heat exchanger c106.In some embodiments, a hot-side heat exchanger c106 and/or aworking-fluid body c108 may provide an improve heating efficiency withthe second combustion zone c407 operating as the primary combustionzone.

As mentioned, in some embodiments, a combustor body c400 may include aplurality of combustion fins c450 circumferentially spaced about theperimeter of the combustion chamber c102 and/or the longitudinal axisc204. The plurality of combustion fins c450 may define a radially orconcentrically inward portion of the plurality of combustion-gaspathways c422. The term “combustion-gas pathway” may refer to theportion of a heating fluid pathway c602 defined by the combustion finsc450. The combustion-gas pathways c422 may be configured and arranged asspirals or spiral arcs, and may be oriented concentrically about thecombustion chamber c102 and/or the longitudinal axis c204. Thecombustion-gas pathways c422 may fluidly communicating with acorresponding plurality of spiral pathways of the hot-side heatexchanger c106. The plurality of combustion fins c450 may respectivelydefine a portion of a corresponding plurality of heating walls c616.Such combustion fins c450 may concurrently define at least a portion ofthe second combustion chamber c448 and at least a portion of thehot-side heat exchanger c106. The second combustion zone c407 may occupyat least part of the radially or concentrically inward portion of theplurality of combustion-gas pathways c422 defined by the plurality ofcombustion fins c450.

Regardless of whether the secondary combustion zone c407 includescombustion fins c450, at least a portion of the combustor body c400proximate to the secondary combustion zone c407 may become red-hot,encouraging a sustained combustion flame within the secondary combustionzone c407. Combustion in the secondary combustion zone c407 may takeplace at an air-to-fuel ratio closer to the stoichiometric air-to-fuelratio, with or without secondary combustion support from the firstcombustion zone c405.

A heater body c100 that includes a multi-stage combustor c403 mayinclude a cool-zone fuel injector c411 and a hot-zone fuel injectorc413. However, in some embodiments, a multi-stage combustor c403 may beconfigured to sustain combustion in a plurality of combustion zones withonly a single fuel injector, such as a cool-zone fuel injector c411 or ahot-zone fuel injector c413. The cool-zone fuel injector c411 may occupya distal position relative to the longitudinal axis c204 of thecombustion chamber c102. The cool-zone fuel injector c411 may occupy aradially or concentrically inward position relative to the longitudinalaxis c204 of the combustion chamber c102. In some embodiments, ahot-zone fuel injector c413 may occupy a proximal position relative tothe longitudinal axis c204 of the combustion chamber c102. The hot-zonefuel injector c413 may occupy a radially or concentrically outwardposition relative to the longitudinal axis c204 of the combustionchamber c102 and/or relative to the radially or concentrically inwardposition of the cool-zone fuel injector c411. The cool-zone fuelinjector c411 may coincide with the first combustion zone c405.Additionally, or in the alternative, the first fuel injector may belocated upstream from the first combustion zone c405. For example, thecool-zone fuel injector c411 may be operably coupled to a combustor capc210, such as at a nozzle port c212. The hot-zone fuel injector c413 maycoincide with the second combustion zone c407. Additionally, or in thealternative, the hot-zone fuel injector c413 may be located upstreamfrom the second combustion zone c407.

In some embodiments, a heater body c100 and/or a combustor body c400 mayinclude one or more fuel injectors monolithically integrated with adistal portion of the combustor body c400 and/or a radially orconcentrically inward portion of the combustor body c400. The one ormore fuel injectors may be monolithically integrated with a radially orconcentrically inward portion of the hot-side heat exchanger c106. Forexample, a plurality of a hot-zone fuel injectors c413 may bemonolithically integrated with a distal portion of the combustor bodyc400 and/or a radially or concentrically inward portion of the pluralityof combustion-gas pathways c616 of the hot-side heat exchanger c106. Theone or more fuel injectors may be monolithically integrated with theplurality of heating walls c616 and/or the plurality of combustion finsc450. Such plurality of hot-zone fuel injectors c413 may operate as acollective unit and may be referred to collectively as a hot-zone fuelinjector c413. Additionally, or in the alternative, such plurality ofhot-zone fuel injectors c413 may operate independently from one anotherand may be referred to individually as a hot-zone fuel injector c413.

One or more hot-zone fuel pathways c415 may be monolithically integratedwith at least part of a distal portion of the combustor body c400 and/ora radially or concentrically inward portion of the hot-side heatexchanger c106. The one or more hot-zone fuel pathways c415 may beconfigured to supply fuel for combustion at the second combustion zonec407. For example, as shown in FIGS. 4.2.2A and 4.2.2.B, a plurality ofhot-zone fuel pathways c415 may be defined within respective ones of aplurality of heating walls c616 of a hot-side heat exchanger c106.Additionally, or in the alternative, one or more hot-zone fuel pathwaysc415 may be defined within a distal portion of the combustor body c400.

As shown, a plurality of heating walls c616 may include a heat sinkc409, such as a hot-side heat exchanger c106 and/or a working-fluid bodyc108. The plurality of heating walls c616 may occupy a radiallyconcentrically outward position relative to the combustion chamber c102.The plurality of heating walls c616 may define a corresponding pluralityof combustion-gas pathways c422, such as spiral pathway or a spiral arcpathway, fluidly communicating with the combustion chamber c402 atcircumferentially spaced locations about the combustion chamber c402.The combustion-gas pathways c422 may fluidly communicate with a proximalportion c200 of the combustion chamber c102. The plurality ofcombustion-gas pathways c422 may follow an annular or semiannular spiraltrajectory relative to the combustion chamber c102 and/or thelongitudinal axis c204 thereof.

The hot-zone fuel pathways c415 may fluidly communicate with respectiveones of a plurality of combustion-gas pathways c422 of the hot-side heatexchanger c106, such as at respective ones of a plurality of heatingwalls c616 and/or combustion fins c450. The plurality of heating wallsc616 and/or combustion fins c450 may have a plurality of openings c451(e.g., pore-like openings) that fluidly communicate with the pluralityof combustion-gas pathways c422 of the hot-side heat exchanger c106 anddefine the hot-zone fuel injectors c413.

In some embodiments, at least a portion of the hot-zone fuel pathwaysc415 may define a vaporization heat exchanger c417 that provides a heattransfer relationship between a combustion flame c426 and fuel withinthe hot-zone fuel pathways c415, and or between hot combustion gas c426fuel within the hot-zone fuel pathways c415. The vaporization heatexchanger c417 may be effective to vaporize fuel (e.g., liquid fuel),such as when the fuel is within the hot-zone fuel pathways c415 and/orthe hot-zone fuel injectors c413, or as the fuel is discharged from theopenings (e.g., the pore-like openings) of the hot-zone fuel injectorsc413.

During operation, heat from the first combustion zone c405 may heat thehot-zone fuel injectors c413 and/or at least a portion of the secondcombustion zone c407 to a sufficiently high temperature to allow fuelflowing out of the hot-zone fuel injectors c413 to auto-ignite. Forexample, a distal portion of the combustion chamber c102, and/or aradially or concentrically inward portion of the hot-side heat exchangerc106 (e.g., the combustion fins c450 and/or a radially or concentricallyinward portion of the heating walls c616) may operate at a sufficientlyhigh temperature to allow fuel flowing out of the hot-zone fuelinjectors c413 to auto-ignite. The flame c426 and/or hot combustion gasc428 may have a temperature of from about 300 C to about 900 C, such asfrom about 350 C to about 800 C, such as from about 425 C to about 750C, such as from about 500 C to 600 C. Once the fuel flowing out of thehot-zone fuel injectors c413 auto-ignites, the flame provided bycool-zone fuel injector c411 may be reduced to a minimal lengthsufficient to support combustion at the second combustion zone c407. Inthis way, the flame from the cool-zone fuel injector c411 may operate asa pilot burner configured to provide a pilot flame, or ignition source,for combustion in the second combustion zone c407. The pilot flame, orignition source, provided by the cool-zone fuel injector c411 maysupport auto-ignition and good combustion of combustion gas c428 and/orfuel c426 flowing from the first combustion zone c405 to the secondcombustion zone c407, for example, providing a reburn combustion regime.Additionally, or in the alternative, such pilot flame, or ignitionsource may support auto-ignition and good combustion of fuel supplied bythe hot-zone fuel injectors c413.

In some embodiments, the first combustion zone c405 may exhibit a richcombustion environment attributable at least in part to the fuel-to-airratio resulting from fuel from the cool-zone fuel injector c411. Thesecond combustion zone c407 may exhibit a lean combustion environmentattributable at least in part to the fuel-to-air ratio resulting fromthe rich combustion environment of the first combustion zone c405 and/orfuel from the hot-zone fuel injectors c413. In some embodiments, thefirst combustion zone c405 may exhibit a lean combustion environmentprior to auto-ignition at the second combustion zone c407. Uponauto-ignition at the second combustion zone c407, the first combustionzone c405 may transition to a rich combustion environment. The secondcombustion zone c407 may thereafter exhibit a lean combustionenvironment while the first combustion zone c405 may exhibit a richcombustion environment.

As mentioned, a lean combustion environment may be characterized by anequivalence ratio, which is the ratio of the actual fuel-to-air ratio tothe stoichiometric fuel-to-air ratio. A rich combustion environment maysimilarly be characterized by an equivalence ratio. An exemplary leancombustion environment may include an equivalence ratio of from about0.5 to about 1.0, such as from about 0.6 to about 0.9, or from about 0.7to about 0.8 An exemplary rich combustion environment may include anequivalence ratio of from less than about 0.1 to about 0.5, such as fromless than about 0.1 to about 0.2. By way of example, the firstcombustion zone c405 may exhibit an aforementioned “lean” equivalenceratio prior to auto-ignition at the second combustion zone c407, such asfrom about 0.5 to about 1.0, or any other suitable lean equivalenceratio. Upon auto-ignition at the second combustion zone c407, the firstcombustion zone c405 may transition to a “rich” equivalence ratio, suchas from less than about 0.1 to about 0.5, or any other suitable richequivalence ratio. The second combustion zone, meanwhile, may exhibit a“lean” equivalence ratio, such as from about 0.5 to 1.0, or any othersuitable lean equivalence ratio. In exemplary embodiments, fuel may besupplied to the cool-zone fuel injector without pre-mix air, forexample, to provide a rich combustion environment.

As shown in FIG. 4.2.2B, in some embodiments, the second combustion zonec407 may occupy one or more regions of the plurality of combustion-gaspathways c422 of the hot-side heat exchanger c106. For example,respective combustion-gas pathways c422 may include a respective secondcombustion zone-segment c407A.

In some embodiments, the combustion-gas pathways c422 may include aburner zone c419 configured to support combustion and/or flamestabilization within the second combustion zone c407 and/or within therespective combustion zone-segments c407A. The burner zone c419 may bedefined by a plurality of burner gap, GB, c421 defined in the respectiveheating walls c616 and oriented along the flowpath of the respectivecombustion-gas pathways c422. The burner gaps c421 may be locateddownstream from the hot-zone fuel injectors c413, such as betweenrespective combustion fins c450 and corresponding downstream portions ofthe heating walls c616. A burner gap c421 may define a gap between acombustion fin c450 and a corresponding heating wall c616. The burnergaps c421 may include an open space, a mesh, a three-dimensionallattice, a porous medium, or the like. The burner zone c419 may coincidewith at least a portion of the second combustion zone c407.Additionally, or in the alternative, the second combustion zone c407 mayat least partially coincide with the plurality of burner gaps c421.

In some embodiments, a combustion chamber c104 may include a vortexconditioner c137, as shown, for example, in FIGS. 4.1.7, 4.2.2A.,4.5.5A, 4.5.5C, and 4.5.5D. The vortex conditioner c137 may bemonolithically integrated with a proximal portion of the combustionchamber c102. The vortex conditioner c137 may be configured at least inpart to establish and/or sustain a vortex flow field that includes thecombustion gas c428 and/or the flame c426. For example, the vortexconditioner c137 may be configured at least in part to establish and/orsustain a bidirectional coaxial vortex flow field, which may enhanceheat transfer of the flame c426 to the hot-side heater body c106 and/ormay protect the combustion chamber wall c406 from receiving excessiveheat from the flame c426. The second combustion zone c407 may occupy aradially or concentrically outward position relative to the vortexconditioner c137. As shown, the vortex conditioner c137 may have aconical or frustoconical shape projecting into the combustion chamberc102, such as along the longitudinal axis c204; however, other shapesare also envisioned. In some embodiments, a conical or frustoconicalshape of the vortex conditioner c137, and/or the location and/ordimensions thereof, may at least partially contribute to the vortex flowfield (e.g., the bidirectional coaxial vortex flow field) of thecombustion gas c428 and/or the flame c426. A vortex conditioner c137 maybe included with a heater body c100 and/or a combustor body c400configured for single-stage and/or multi-stage combustion.

Now referring to FIGS. 4.2.3A-4.2.3C, further exemplary combustor bodiesc400 will be described. As shown in FIG. 4.2.3A, an exemplary combustorbody c400 may include a venturi c423 in the conditioning conduit pathwayc416, such as at a distal portion c202 of the conditioning conduit c122.The combustor body c400 may have a frustoconical configuration. Forexample, the conditioning conduit c122 may have a frustoconicalconfiguration. Additionally, or in the alternative, the combustionchamber c102 may have a frustoconical configuration. The venturi c423may be effective to improve mixing and/or reduce pressure drop in fluidflow through the conditioning conduit pathway c416 as the flowtransitions form the conditioning conduit pathway c416 to the combustionchamber c102. The venturi c423 may additionally or alternatively induceturbulence, providing a mixing zone for fuel entering the combustionchamber c102 from a fuel nozzle c126, such as a cool-zone fuel injectorc111. The venturi c423 may additionally or alternatively accelerate flowinto the combustion chamber, such as into the first combustion zonec405. Such improved mixing, reduced pressure drop, and/or flowacceleration may increase combustion efficiency and/or heatingefficiency of the heater body c100.

As shown in FIG. 4.2.3B, the venturi provides an increase in velocity asthe flow of combustion gas and/or intake air along the conditioningconduit pathway c416 transitions form zone “A” to zone “B” at thetransition from the conditioning conduit c122 to the combustion chamberc102. The velocity of the flow decreases as the flow advances towardszone “C” within the combustion chamber c102. The venturi c423 may workin cooperation with a Coanda surface c424 to condition flow into thecombustion chamber c102. A smoothly converging and diverging flowpathmay be effective to reduce pressure drop across the venturi c423.

As shown in FIG. 4.2.3C, in some embodiments, the flow of combustion gasand/or intake air in the conditioning conduit pathway c416 may exhibit atangential velocity gradient that increases from a radially orconcentrically inward portion to a radially or concentrically outwardportion of the conditioning conduit pathway c416. The tangentialvelocity gradient may increase as the radius of the conditioning conduitpathway c416 decreases, for example, as the conditioning conduit pathwayc416 approaches the venturi c423. Such increase in velocity attributableto the tangential velocity gradient may further enhance mixing at zone“B,” shown in FIGS. 4.2.3A and 4.2.3B, such as at the venturi c423.

The frustoconical configuration and arrangement of the combustor bodyc400, including the configuration and arrangement of the conditioningconduit c122 and/or the combustion chamber c102, may be selected atleast in part to provide a desired reduction in pressure drop, fluidflow rate, and/or size of the combustor body. For example, pressure dropmay be reduced by providing a small convergence angle, θ c425. Bycontrast, a small convergence angle may correspond to a taller combustorbody c400, increasing material cost. Conversely, a large convergenceangle, θ c425 may allow for a shorter combustor body c400 but increasedpressure drop. These factors may be balanced to determine a suitablefrustoconical configuration and arrangement for the combustor body c400.

Now turning to FIGS. 4.2.4A-4.2.4E, in some embodiments, a combustorbody c400 may include one or more combustor vanes c427. The combustorvanes c427 may be configured to condition a flow of combustion gasand/or intake air into the combustion chamber. In some embodiments, thecombustor vanes c427 may be configured to induce a vortex or turbulentflow in combustion gas and/or intake air entering the combustionchamber. Such vortex or turbulent flow may improve mixing, for example,providing a mixing zone for fuel entering the combustion chamber 102from a fuel nozzle c126, such as a cool-zone fuel injector c111. Thecombustor vanes c427 may be fixed to the combustor cap c210. Forexample, the combustor vanes c427 may define a monolithic portion of thecombustor cap c210. Additionally, or in the alternative, a combustionchamber c102 may include one or more combustor vanes c427, for example,defining a monolithic portion of the combustion chamber c102.

In some embodiments, a plurality of vane rows may be provided. Forexample, as shown, a combustor body c400 and/or a combustor cap c210 mayinclude three vane rows. As shown in FIG. 4.2.4A, a combustor cap c210may include a first vane row c429A, a second vane row c429B, and/or athird vane row c429C. The respective vane rows may include one or morevanes. The vane rows may be oriented coannularly relative to alongitudinal axis of the combustor body c204.

The first vane row c429A may define a shield flowpath along the wall ofthe combustion chamber c102. The shield flowpath may provide cooling tothe combustion chamber wall. The second vane row c429B may provide amain flowpath. The main flowpath may provide the bulk flow forcombustion. The third vane row c429C may provide a premixing flowpath.The premixing flowpath may provide oxygen to mix with fuel prior tocombustion.

The respective combustor vanes c427 may have any desired configuration.A combustor vane c427 may have any desired height extending from aninward combustor cap-surface c431. A combustor vane c427 may have aheight that runs parallel to the inward combustor cap-surface c431.Additionally, or in the alternative, a combustor vane c427 may have aheight that is sloped relative to the inward combustor cap-surface 431.By way of example, FIG. 4.2.4B shows an individual combustor vane c427that has a sloped height relative to the inward combustor cap surfacec431.

By way of example, FIGS. 4.2.4C-4.2.4E show exemplary configurations ofcombustor vanes c427. The configurations shown are provided by way ofexample and not to be limiting. As shown in FIG. 4.2.4C, a plurality ofcombustor vanes c427 may have an airfoil-type configuration.Additionally, or in the alternative, a plurality of combustor vanes c427may have a baffle-type configuration. A plurality of rows ofairfoil-type combustor vanes c427 and/or baffle-type combustor vanesc427 may be provided, such as three rows, as shown. A plurality ofcombustor vanes c427 may additionally or alternatively have a spiralconfiguration, as shown, for example, in FIG. 4.2.4E.

Now turning to FIGS. 4.2.5A and 4.2.5B, exemplary methods of combustinga fuel will be described. Exemplary methods may be performed inconnection with operation of a combustor body c400, a heater body c100,and/or a closed-cycle engine c002 as described herein. As shown in FIG.4.2.5A, an exemplary method c470 may include, at block c472, swirlingcombustion gas through a conditioning conduit c122, with the combustiongas flowing from a proximal portion of the conditioning conduit c122 toa distal portion of the conditioning conduit c122 while swirling. Atblock c474, the exemplary method c470 may include swirling thecombustion gas through a combustion chamber c102. In the exemplarymethod c470, the conditioning conduit c122 may circumferentiallysurround the combustion chamber c102 with the conditioning conduit c122providing fluid communication with the combustion chamber c102 at adistal portion of the combustion chamber c102. The combustion gas mayflow from the distal portion of the conditioning conduit c122 to thedistal portion of the combustion chamber c102 and from the distalportion of the combustion chamber c102 to a proximal portion of thecombustion chamber c102. At block c476, the exemplary method c470 mayinclude combusting a fuel c426 in the combustion chamber c102. The fuelmay be supplied at least in part from the combustion gas flowing fromthe conditioning conduit c122 to the combustion chamber c102.

The exemplary method c470 may additionally or alternatively include, atblock 478, supplying at least a portion of the fuel to the combustionchamber c102 through a fuel nozzle c214 fluidly communicating with adistal portion of the combustion chamber c102. Additionally, or in thealternative, the exemplary method c470 may include supplying at least aportion of the fuel to the combustion chamber through the conditioningconduit. For example, the exemplary method c470 may include, circulatingat least a portion of the combustion gas through one or moreconditioning conduit inlets c414 disposed about a proximal portion ofthe conditioning conduit.

At block c480, the exemplary method c470 may include circulating atleast a portion of the combustion gas through a recirculation pathwayc104, with the recirculation pathway c104 providing fluid communicationfrom a proximal portion of the combustion chamber c102 to a proximalportion of the conditioning conduit c122. The recirculation pathway c104may include a hot-side heat exchanger c106 and a recirculation eductorc116. The hot-side heat exchanger c106 may fluidly communicate with aproximal portion of the combustion chamber c102 and the recirculationeductor c116 may fluidly communicate with a downstream portion of thehot-side heat exchanger c106 and a proximal portion of the conditioningconduit c122 and/or and a distal portion of the combustion chamber c102.The exemplary method may include combusting at least a portion of thecombustion gas circulating through the recirculation pathway c104.

At least a portion of the fuel may be supplied to the combustion chamberc102 through one or more conditioning conduit inlets c414 disposed abouta proximal portion of the conditioning conduit c122. Supplying fuelthrough the one or more conditioning conduit inlets c414 may includesupplying fuel through one or more motive pathways c418 and/or one ormore eduction pathways c420. The one or more conditioning conduit inletsc414 may be oblique to the conditioning conduit c122, for example, tofacilitate swirling of the combustion gas and/or fuel.

Now referring to FIG. 4.2.5B, another exemplary method c471 ofcombusting a fuel will be described. As shown, an exemplary method c471may include, at block c473, combusting a fuel at a first combustion zonec405; at a block c475, heating a second combustion zone c407; and, atblock c477, combusting a fuel at the second combustion zone c407. Insome embodiments, an exemplary method c471 may include, at block c479,auto-igniting fuel at the second combustion zone c407. Combusting thefuel at a first combustion zone c405 may include, at block c481,combusting fuel from a cool-zone fuel injector c411 at the firstcombustion zone c405. Auto-igniting fuel at the second combustion zonec407 may include, at block c483, auto-igniting fuel from the cool-zonefuel injector c411 from a hot-zone fuel injector c413 at the secondcombustion zone c407. Combusting the fuel at the second combustion zonec407 may include, at block c485, combusting fuel from the cool-zone fuelinjector c411 and/or from the hot-zone fuel injector c413 at the secondcombustion zone c407. Heating the second combustion zone c407 mayinclude, at block c487 vaporizing fuel in a vaporization heat exchangerc417.

In some embodiments, combusting fuel at the first combustion zone c405may include, at block c489, combusting fuel at the first combustion zonec405 in a lean combustion environment and/or a rich combustionenvironment. At block c491, combusting fuel at the second combustionzone c407 may include combusting fuel at the second combustion zone c407in a rich combustion environment. In some embodiments, an exemplarymethod c471 may include, at bock c493A, combusting fuel at the firstcombustion zone in a lean combustion environment, and, at block c493B,combusting fuel at the first combustion zone in a rich combustionenvironment upon having auto-ignited fuel at the second combustion zone.At block c491C, an exemplary method c471 may include combusting fuel atthe second combustion zone in a lean combustion environment whilecombusting fuel at the first combustion zone in a rich combustionenvironment.

Any one or more parameters may be utilized to control one or moreoperations of a combustor body c400, a heater body c100, and/or aclosed-cycle engine c002 as described herein, including one or moreoperations in connection with methods of combustion a fuel such as theexemplary methods described herein with reference to FIGS. 4.2.5A and4.2.5B. By way of example, an exemplary method of combustion a fuelc470, c471 may include controlling one or more of: a fuel flow (e.g., afuel flow to a cool-zone fuel injector c411 and/or a hot-zone fuelinjector c413), an air flow (e.g., an intake airflow, an exhaust flow,and/or a combustion gas flow).

Fuel injectors for relatively small or compact apparatuses such asexternal or internal combustion engines for automotive vehicles,watercraft, or light aircraft, or power units, are limited in spacedsuch as to inhibit provision of dual-fuel systems. As such, there is aneed for fuel injector assemblies that provide dual-fuel systems forrelatively small or compact apparatuses.

Embodiments of a fuel injector assembly are provided that may improveatomization and ignition of two or more fuels flowed from the fuelinjector assembly. The embodiments shown and described provide a secondfuel circuit, through which a liquid or gaseous fuel flows, surroundedat a downstream end by one or more gaseous fluid circuits, such as toprovide cooling at the second fuel circuit to mitigate coking and fuelinjector deterioration. The fuel injector assembly provided hereinprovides a compact assembly that may provide dual-fuel combustion forautomotive, marine, auxiliary power unit, rotary or fixed wing aircraft,or other vehicles necessitating smaller combustion assemblies.

Referring now to FIG. 4.3.1, a cross sectional view of an exemplaryembodiment of a fuel injector assembly d100 (“fuel injector d100”) isgenerally provided. The body d110 of the fuel injector d110 is extendedalong a lateral direction L between an upstream end d99 and a downstreamend d98. A reference fuel injector centerline axis d13 is definedthrough a cylindrical portion d116 of the body d110. The cylindricalportion d116 of the body d110 is defined circumferentially relative tothe reference centerline axis d13 and extended along the lateraldirection L. The body d110 further includes a frustoconical portion d117at the downstream end d98.

The fuel injector d100 includes a first fuel circuit d111 and a secondfuel circuit d112 each defined within the body d110. The first fuelcircuit d111 and the second fuel circuit d112 are each extended alongthe lateral direction L from the upstream end d99 to the downstream endd98.

Referring still to FIG. 4.3.1, in various embodiments, the first fuelcircuit d111 and the second fuel circuit d112 each extend along alateral distance d120 of the body d110. The lateral distance d120 of thebody d110 is extended from the downstream end d98 (i.e., at a tipcorresponding to an output port d105) to the upstream end d99 (i.e.,corresponding to an inlet port d108). For a portion of the lateraldistance d120, such as depicted at reference dimension d121 extendedfrom the downstream end d98, the first fuel circuit d111 is extendedannularly within the body d110. For another portion of the lateraldistance d120, such as depicted at reference dimension d122 extendedfrom the downstream end d98, the second fuel circuit d112 is extendedannularly within the body d110. In various embodiments, the portion d121of the lateral distance d120 for which the first fuel circuit d111 isextended circumferentially through the body d110 is greater than theportion d122 of the lateral distance d120 for which the second fuelcircuit d112 is extended circumferentially through the body d110. In oneembodiment, the portion d122 is 90% or less of the portion d121. Inanother embodiment, the portion d122 is 75% or less of the portion d121.In still another embodiment, the portion d122 is 50% or less of theportion d121. In various embodiments, the portion d122 is 33% or greaterof the portion d121.

Referring now to FIG. 4.3.8, another cross sectional view of anexemplary embodiment of the fuel injector d100 is provided. In FIG.4.3.8, the fuel injector d100 further includes an igniter d140 extendedthrough an outlet port d105 through the downstream end d98 of the bodyd110. In various embodiments, the outlet port d105 is extended throughthe body d110 concentric to the reference centerline axis d13. Theigniter d140 may be extended through a cavity d133 radially orconcentrically inward of the fuel circuits d111, d112 and extendedlaterally within the body d110. In particular embodiments, the igniterd140 may extend through the cavity d133 from the upstream end d99 of thebody d110 through an inlet port d108 to admit the igniter d140 into thecavity d133 and protrude from the downstream end d98 of the body d110into a combustion chamber. The igniter d140 extends through the outletport d105 such as to dispose the downstream end d98 of the igniter d140to one or more of the flows of fuel d101, d102 egressed from theirrespective fuel circuits d111, d112.

In various embodiments, the igniter d140 provides an energy source toignite and combust the flows of fuel d101, d102 egressed from theirrespective fuel circuits d111, d112. In one embodiment, the igniter d140defines a glow plug such as to provide a source of thermal energy suchthat when one or more flows of fuel d101, d102 are exposed to heatgenerated from the igniter d140 causes the fuel d101, d102 to ignite. Inparticular embodiments, the second flow of fuel d102 defining a liquidfuel is exposed to heat generated from the igniter d140 to cause thefuel d102 to ignite.

A method for operation of the fuel injector d100 is provided herein inwhich a relatively low pressure second flow of fuel d102 is providedthrough a second fuel inlet opening d107 (FIGS. 4.3.1 and 4.3.8) to thesecond fuel circuit d112. The relatively low pressure second flow offuel d102 egresses from the body d110 of the fuel injector d100 via thesecond fuel injection opening d125. As the egressed fuel d102 flowscloser to or touches the igniter d140, it is initially ignited (e.g.,light-off) and may further ignite the first flow of fuel d101 egressedfrom the plurality of first fuel injection apertures d115. Followinglight-off, the pressure may increase such as to improve atomization anddesirably alter combustion and heat release characteristics, such as toimprove operability, performance, and reduce emissions output (e.g.,smoke, unburned hydrocarbons, oxides of nitrogen, etc.).

The igniter d140 included through the body d110 of the fuel injectord100 may provide and/or improve providing dual fuel (i.e., the first andsecond flows of fuel d101, d102) operation of the fuel injector d100 atrelatively small engine apparatuses, such as those for external orinternal combustion engines, including those for automotive, personal orlight water craft, or auxiliary power unit applications.

In still various embodiments, during operation of the fuel injectord100, the first flow of fuel d101 defining a gaseous fuel is providedthrough a first inlet opening d106 (FIGS. 4.3.1 and 4.3.8) to the firstfuel circuit d111. The fuel d101 egresses from the body d110 through theplurality of first fuel injection apertures d115 for combustion.

Embodiments of the fuel injector d100 shown and depicted herein inregard to FIGS. 4.3.1 and 4.3.8 may be constructed via one or moremanufacturing processes known in the art. In various embodiments, thefuel injector d100 may be constructed as a single, unitary construction.In another embodiment, the body d110 may be constructed as a single,unitary construction separate from the igniter d140. Manufacturingprocesses for constructing the fuel injector d100 may include one ormore processes generally referred to as additive manufacturing or 3Dprinting. Additionally, or alternatively, manufacturing processes forconstructing the fuel injector d100 may include one or more machiningprocesses or other material removal processes, material additiveprocesses such as welding, brazing, soldering, or bonding processesgenerally, or one or more casting or forming processes.

In still various embodiments, the fuel injector d100 may include one ormore materials appropriate for fuel injection to a combustion chamber,such as, but not limited to, iron or iron-based materials, aluminum,magnesium, nickel, titanium, ceramic or metal matrix composites, oralloys or combinations thereof, or other materials appropriate forcombustion systems. Furthermore, the fuel injector d100 may include oneor materials appropriate for heat engines generally, or external orinternal combustion engines, closed-cycle engines, Stirling cycle,Rankine cycle, or Brayton cycle machines more specifically.

Embodiments of the fuel injector d100 provided herein may be configuredto receive and desirably inject a plurality of types of fuels throughthe first circuit d111 and the second circuit d112. Exemplary fuelsinclude, but are not limited to, propane, ethane, coke oven gas, naturalgas, synthesis gas, liquid fuel such as diesel fuel, gasoline, syntheticfuel, or a plurality of specifications of kerosene or jet fuel (e.g.,Jet A, JP-8, etc.), or mixtures of gaseous and/or liquid fuels thereof.

A method for operation of the fuel injector d100 provides forselectively relatively low pressure/flow output and high pressure/flowoutput of fuel through each circuit d111, d112, d113 of the fuelinjector d100. The fuel injector d100 provides for a relatively lowpressure/flow operation of the fuel injector d100 for a first flow offuel to egress from the fuel injector d100 and touch the hot igniterd140, such as defining glow plug, to ignite the fuel. The fuel injectord100 further provides for a relatively high pressure/flow operation ofthe fuel injector d100 for the first flow of fuel, or additionally oralternatively, a second flow of fuel, to egress the fuel injector d100such as to avoid touching the igniter d140. As such, the relatively highpressure/flow operation of the fuel injector d100 prevents undesiredburn-up, wear, or other deterioration of the igniter d140. The highpressure/flow operation of the fuel injector d100 may additionally, oralternatively, provide the second flow of fuel (e.g., via the secondcircuit d112) to generate a buffer, such as a fluid and/or thermalbreak, between the first flow of fuel from the first circuit d111 andthe igniter d140. In still various embodiments, the first flow of fuelfrom the first circuit d111 defines a liquid fuel. The second flow offuel from the second circuit d112 may define a liquid and/or gaseousfuel. In still other embodiments, one or more other fluids, such as anon-fuel fluid, may be provided through the first circuit d111, thesecond circuit d112, and/or the third circuit d113. In one embodiment,the fluid provided through the fuel injector d100 includes an inert gas,urea, or other substance such as to desirably control emissions, providea thermal or fluid barrier, or clean one or more circuits or passages ofthe fuel injector d100. For example, urea may be added to the fuel suchas to decrease emissions associated with diesel fuels or similar.

In still various embodiments, the fuel injector d100 provides astructure and method for operation at which the vane structure d130provides or generating a circumferential swirl to the fuel throughsecond circuit d112, such as described herein. In one embodiment, themethod for operation includes providing a circumferential swirl to aliquid fluid or fuel via the vane structure d130 within the secondcircuit d112. The liquid fuel then egresses the fuel injector d100 viathe respective opening(s) with at least a partial circumferentialvelocity component, such as depicted in regard to FIG. 4.3.1.

In another embodiment, the structure and method for operation includesproviding or generating a substantially no-swirl or axial flow of fuelthrough the second circuit d112 via the vane structure d130 such asdescribed herein. In one embodiment, the method for operation includesproviding the gaseous fluid or fuel through a first upstream vanestructure d130 relative to a second downstream vane structure d130. Thesecond downstream vane structure d130 defines at least one openingcircumferentially offset from an opening defined at the first upstreamvane structure d130. In one embodiment, the method may include providinga single opening at the first upstream vane structure d130 and a singleopening at the second downstream vane structure d130. The vane structured130 may further provide for retarding a circumferential flow componentof the fluid via the circumferentially offset opening defined at eachvane structure d130. The method may further include egressing the flowof fuel via respective opening(s) with a substantially no-swirl ornon-circumferential flow component. The substantially non-swirl flow ofgaseous fluid may provide improved thermal and/or fluid barrier betweenthe igniter d140 and the combustion gases radially or concentricallyoutward or surrounding the igniter d140.

Embodiments of the fuel injector d100 provided herein may providerelatively low pressure supply of the fuels d101, d102 through the fuelinjector d100 for egress through the plurality of first fuel injectionapertures d115 and second fuel injection opening d125 and combustion ata combustion chamber. In one embodiment, the fuel injector d100 providedherein may provide the second flow of fuel d102 defining a liquid fuelto be provided through the fuel injector d100 without a fuel pump. Forexample, the fuel injector d100 may receive the second flow of fuel d102via header pressure from a fuel tank providing the second flow of fueld102. Generally, as the fuel injector d100 provided herein may operatewith relatively low pressure fuel sources, dual-fuel fuel injectors d100may be provided to apparatuses typically too small or compact fordual-fuel systems, such as, but not limited to, external or internalcombustion engines for automotive vehicles, personal or commercialmarine vehicles, personal watercraft, light aircraft, including shorttakeoff and vertical landing (STOVL) vehicles, rotary or fixed wingaircraft, or auxiliary power units.

Now referring to FIGS. 4.4.1A and 4.4.1B, 4.4.2A and 4.4.2B, and 4.4.3Aand 4.4.3B, exemplary heat exchanger bodies c600 (e.g., hot-side heatexchanger bodies c600) will be described. The presently disclosedhot-side heat exchanger bodies c600 may define part of a heater bodyc100 and/or a closed-cycle engine c002. For example, a hot-side heatexchanger body c600 may define at least a portion of a monolithic bodyor a monolithic body-segment. Such monolithic body or monolithicbody-segment may define at least a portion of the heater body c100and/or the closed-cycle engine c002. Additionally, or in thealternative, the presently disclosed hot-side heat exchanger bodies c600may be provided as a separate component, whether for use in connectionwith a heater body c100, a closed-cycle engine c002, or any othersetting whether related or unrelated to a heater body c100 or aclosed-cycle engine c002. At least a portion of the hot-side heatexchanger body c600 may define a hot-side heat exchanger c106. While theheater bodies c100 depicted in the figures may show one hot-side heatexchanger body c600 and/or one hot-side heat exchanger c106, it will beappreciated that a heater body c100 may include a plurality of hot-sideheat exchanger bodies c600 and/or a plurality of hot-side heatexchangers c106. For example, a heater body c100 may include one or morehot-side heat exchanger bodies c600, and/or a hot-side heat exchangerbody c600 may include one or more hot-side heat exchangers c106.

As shown, a hot-side heat exchanger body c600 and/or a hot-side heatexchanger c106 may include a plurality of heating walls c616. Theplurality of heating wall c616 may be configured and arranged as anarray of heating walls c616. The heating walls c616 may be radially orconcentrically adjacent to one another. The heating walls c616 may beconfigured and arranged as a spiral or a spiral arc, and may be disposedannularly or semi-annularly relative to the combustion chamber c102and/or the longitudinal axis c204 thereof. The heating wall c616 may beconcentrically nested with one another. The heating wall c616 may beconfigured and arranged as an array of substantially concentric spiralsand/or an array of substantially concentric spiral arcs. By way ofexample, a spiral or spiral arc, such as in an array of substantiallyconcentric spirals or spiral arcs, may correspond to at least a portionof an Archimedean spiral, a Cornu spiral, a Fermat's spiral, ahyperbolic spiral, a logarithmic spiral, a Fibonacchi spiral, aninvolute, or a squircular spiral, as well as combinations of these.

The heating walls c616 define a plurality of heating fluid pathwaysc602. The heating fluid pathways c602 may make up a portion of thehot-side heat exchanger body c600 and/or a hot-side heat exchanger c106,defining a pathway through which a heating fluid such as circulatingcombustion gas may flow. The heating fluid pathways c602 may fluidlycommunicate with an inlet plenum c604. The inlet plenum may include acombustion chamber c602. The heating fluid pathways c602 may beconfigured and arranged as an array of heating fluid pathways c602. Theheating fluid pathways c602 may be radially or concentrically adjacentto one another with a heating wall c616 disposed between respectiveadjacent heating fluid pathways c602. The heating walls c616 may beradially or concentrically adjacent to one another with a heating fluidpathway c602 disposed between respective adjacent heating walls c616.The heating walls c616 may be configured and arranged as a spiral or aspiral arc, and may be disposed annularly or semi-annularly relative tothe combustion chamber c102 and/or the longitudinal axis c204 thereof.The heating fluid pathways c602 may be concentrically nested with oneanother. The heating fluid pathways c602 may be configured and arrangedas an array of substantially concentric spirals and/or an array ofsubstantially concentric spiral arcs. The hot-side heat exchanger bodyc600 may include an array of alternating heating walls c616 and heatingfluid pathways c602.

Upstream ends of the heating walls c616 may be circumferentially spacedabout an inlet plenum c604, such as a combustion chamber. Upstream endsof the heating fluid pathways c602 may respectively define an inletc606, which may be circumferentially spaced about the inlet plenum c604,such as the combustion chamber c102. At least some of the inlets c606may be oriented oblique to the inlet plenum c604. At least some of theplurality of heating fluid pathways c602 may define a spiral pathway.

The inlet plenum c604, such as the combustion chamber c102, may fluidlycommunicate with the plurality of heating fluid pathways c602. Theplurality of heating fluid pathways c604 may respectively define aninlet c606 circumferentially spaced about the inlet plenum c604 (and/ordisposed radially about the inlet plenum c604). Respective ones of theplurality of heating fluid pathways c604 may define respective ones of aplurality of inlets c606. The plurality of inlets c604 may becircumferentially spaced about the inlet plenum c604 (and/or disposedradially about the inlet plenum c604). For example, the plurality ofinlets c604 may be circumferentially spaced about the combustion chamberc102 (and/or disposed radially about the combustion chamber c102). Insome embodiments, respective ones of the plurality of inlets may definerespective ones of a plurality of combustion chamber outlets c412.Additionally, or in the alternative, the inlet plenum c604 may define aplurality of inlets c606 fluidly communicating with respective ones ofthe plurality of heating fluid pathways c602. For example, thecombustion chamber c102 may define a plurality of combustion chamberoutlets c412 and/or a plurality of inlets c606 fluidly communicatingwith respective ones of the plurality of heating fluid pathways c602.

The plurality of heating fluid pathways c602 may additionally oralternatively fluidly communicate with one or more outlet plenum c608,such as a recirculation annulus c208. The fluid communication betweenthe plurality of heating fluid pathways c602 and the one or more outletplenum c608, such as a recirculation annulus c208 may be at a downstreamportion of respective ones of the plurality of heating fluid pathwaysc602. The outlet plenum c608 or recirculation annulus c208 maycircumferentially surround at least a portion of the hot-side heatexchanger body c600 and/or the hot-side heat exchanger c106. Forexample, the outlet plenum c608 or recirculation annulus c208 maycircumferentially surround at least a portion of the plurality ofheating fluid pathways c602.

As shown, for example, in FIGS. 4.4.1B and 4.4.2B, the hot-side heatexchanger body c600 and/or a working-fluid body c108 may define aplurality of heat transfer regions c612. The plurality of heat transferregions c612 may correspond to respective portions of a working-fluidbody c108. A respective heat transfer region c612 may encompass aportion of the hot-side heat exchanger body c600 and/or a portion of theworking-fluid body c108. Respective ones of the plurality of heattransfer regions c612 have a thermally conductive relationship with acorresponding portion c614 of the plurality of heating fluid pathwaysc602, such as a semiannular portion c614 of the plurality of heatingfluid pathways c602. Respective ones of the plurality of heat transferregions c612 may include a heat input region, at least one heatextraction region, and a plurality of working-fluid pathways c110. Theheat input region may include a piston body c700 and the heat extractionregion may include a regenerator body c800.

In some embodiments, a heat transfer region c612 may include at last aportion of a working-fluid body c108. For example, a heat transferregion c612 may include at least a portion of a piston body c700 and/orat least a portion of a regenerator body c800. Additionally, or in thealternative, a heat transfer region c612 include one or moreworking-fluid pathways c110 that have a thermally conductiverelationship with a corresponding portion c614 (e.g., a semiannularportion) of at least some of the plurality of heating fluid pathwaysc602. For example, the heat transfer region c612 may include one or moreworking-fluid pathways c110 defined at least in part within acorresponding one or more heating wall c616 of a hot-side heat exchangerc106. Such working-fluid pathways c110 may define a pathway for anengine-working fluid to flow through the hot-side heat exchanger c106,such as through the one or more heating walls c616 thereof. Where aworking-fluid pathway c110 flows through a hot-side heat exchanger c106,the heat transfer region c612 may include a portion of the working-fluidpathway within or defined by the hot-side heat exchanger c106, such aswithin a region of one or more heating wall c616 of the hot-side heatexchanger c106 corresponding to the heat transfer region c612.

The hot-side heat exchanger body c600 may include a plurality ofworking-fluid pathways c110 monolithically formed within the pluralityof heating walls c616. The plurality of working-fluid pathways may begrouped into an array of working-fluid pathways c110 and/or a pluralityof arrays of working fluid-pathways c110. An array of working-fluidpathways c110 may define a heat transfer region c612. A plurality ofarrays of working-fluid pathways c110 may define a correspondingplurality of heat transfer regions c612. Respective ones of theplurality of arrays of working-fluid pathways c110 may becircumferentially spaced about the hot-side heat exchanger body c600.Respective ones of the plurality of heat transfer regions c600 may becircumferentially spaced about the hot-side heat exchanger body c600.

As shown, for example, in FIGS. 4.4.2A and 4.4.2B, at least some of theworking-fluid pathways c110 may be radially or concentrically adjacentto one another. Additionally, or in the alternative, as also shown, atleast some of the working-fluid pathways c110 may be semiannular to oneanother. The working-fluid pathways c110 may fluidly communicate betweenthe heat input region and the at least one heat extraction region. Theplurality of heating fluid pathways c602 may be disposed radially orconcentrically adjacent to corresponding respective ones of theplurality of working-fluid pathways c110, such as radially orconcentrically adjacent to respective ones of a plurality of semiannularworking-fluid pathways c110. Respective ones of the plurality of heatingfluid pathways c602 may have a thermally conductive relationship withcorresponding respective ones of the plurality of working-fluid pathwaysc110.

The plurality of heat transfer regions c612 may be circumferentiallyspaced about the hot-side heat exchanger body c600. The semiannularportion c614 of the plurality of heating fluid pathways c602corresponding to a respective heat transfer region c612 may correspondto a radial position of the respective heat transfer region c612. Forexample, the plurality of heating fluid pathways c602 may define aspiral pathway, spiraling annularly or semi-annularly around alongitudinal axis, A, c214. The portion c614 of the plurality of headingfluid pathways c602 passing the radial position of a respective heattransfer region c612 may define the semiannular portion c614 of theplurality of heating fluid pathways c602 corresponding to the respectiveheat transfer region c612.

In some embodiments, the plurality of heating fluid pathways c602 maypass adjacent to at least some of the plurality of heat transfer regionsc612 in circumferential series. For example, the plurality of heatingfluid pathways c602 may have a thermally conductive relationship withthe at least some of the plurality of heat transfer regions c612, andthe particular heat transfer region c612 with which a respective portionc614 of the plurality of heating fluid pathways c604 has a thermallyconductive relationship may transition radially from one heat transferregion c612 to and adjacent heat transfer region c612. Thecircumferential series of a respective one of the plurality of heatingfluid pathways c602 may have a sequence depending at least in part on acircumferential location of an inlet c606 to the respective one of theplurality of heating fluid pathways c602.

By way of example, a first heating fluid pathway c618 may pass adjacentto at least some of the plurality of heat transfer regions c612 in afirst circumferential series that includes a first heat transfer regionc620 followed by a second heat transfer region c622. The firstcircumferential series may additionally or alternatively include thesecond heat transfer region c622 followed by a third heat transferregion c624 and/or a fourth heat transfer region c626. For example, thefourth heat transfer region c626 may be preceded by the third heattransfer region c624. A second heating fluid pathway c628 may passadjacent to at least some of the plurality of heat transfer regions c612in a second circumferential series. The second circumferential seriesmay include the second heat transfer region c622 followed by the thirdheat transfer region c624. The second circumferential series mayadditionally or alternatively include the third heat transfer regionc624 followed by the fourth heat transfer region c626 and/or the firstheat transfer region c620. For example, the first heat transfer regionc620 may be preceded by the fourth heat transfer region c626. A thirdheating fluid pathway c630 may pass adjacent to at least some of theplurality of heat transfer regions c612 in a third circumferentialseries. The third circumferential series may include the third heattransfer region c624 followed by the fourth heat transfer region c626.The third circumferential series may additionally or alternativelyinclude the fourth heat transfer region c626 followed by the first heattransfer region c620 and/or the second heat transfer region c622. Forexample, the second heat transfer region c622 may be preceded by thefirst heat transfer region c620. A fourth heating fluid pathway c632 maypass adjacent to at least some of the plurality of heat transfer regionsc612 in a fourth circumferential series. The fourth circumferentialseries may include the fourth heat transfer region c626 followed by thefirst heat transfer region c620. The fourth circumferential series mayadditionally or alternatively include the first heat transfer regionc620 followed by the second heat transfer region c622 and/or the thirdheat transfer region c624. For example, the third heat transfer regionc624 may be preceded by the second heat transfer region c622.

During operation, heating fluid such as combustion gas flowing throughthe plurality of heating fluid pathways c602 may transfer heat to anyone or more of the plurality of heat transfer regions c612. The rate orquantity of heat transferring from the heating fluid to a heat transferregion c612 may vary as between respective ones of the heat transferpathways c602 and/or as between respective ones of the heat transferregions c612. For example, the rate or quantity of heat transferringfrom the heating fluid to a heat transfer region c612 may depend atleast in part on a temperature gradient between the heating fluid andthe heat transfer region, such as a temperature gradient between theheating fluid and the engine-working fluid. In some embodiments,however, the heating fluid within the plurality of heating fluidpathways c602 may exhibit a temperature that differs as between at leasttwo portion c614 (e.g., at least two semiannular portion) correspondingto respective heat transfer regions c612 and/or as between at least twoheating fluid pathways c602 within a given portion c614 (e.g., within asemiannular portion) corresponding to a given heat transfer regionsc612. Additionally, or in the alternative, the plurality of heattransfer regions c612 may exhibit a temperature that differs as betweenat least two heat transfer regions c612. For example, the engine-workingfluid within the plurality of working-fluid pathways c110 correspondingto respective ones of the heat transfer regions c612 may exhibit atemperature that differ as between at least two heat transfer regionsc612 and/or as between at least two working-fluid pathways c110 within agiven heat transfer region c612.

In some embodiments, the temperature of a heating fluid such as acombustion gas may decrease as the heating fluid flows through theplurality of heating fluid pathways c602 and heat transfers from theheating fluid to the heat transfer regions c612 of the working-fluidbody c108, such as from the heating fluid to engine-working fluid in theworking-fluid pathways c110. However, with the plurality of heatingfluid pathways c602 defining a spiral pathway, as shown for example inFIGS. 4.4.1A through 4.4.2B, respective ones of the plurality of heatingfluid pathways c602 may encounter the respective ones of the pluralityof heat transfer regions c612 in a differing sequence, which may dependat least in part on a circumferential location of an inlet c606 to therespective one of the plurality of heating fluid pathways c602.

For example, a first heating fluid pathway c618 may initially encounterthe first heat transfer region c620, such as according to a firstcircumferential series, while a second heating fluid pathway c628 mayencounter the first heat transfer region c620 last, such as according toa second circumferential series. Additionally, or in the alternative, athird heating fluid pathway c630 may encounter the first heat transferregion c620 third in series, such as according to a thirdcircumferential series, and/or a fourth heating fluid pathway c632 mayencounter the first heat transfer region c620 second in series, such asaccording to a fourth circumferential series.

As another example, the second heat transfer region c622 may have athermally conductive relationship with the first heating fluid pathwayc618 occurring second, such as according to the first circumferentialseries. The second heat transfer region c622 may have a thermallyconductive relationship with the second heating fluid pathway c628occurring first, such as according to the second circumferential series.The second heat transfer region c622 may have a thermally conductiverelationship with the third heating fluid pathway c630 occurring last,such as according to the third circumferential series. The second heattransfer region c622 may have a thermally conductive relationship withthe fourth heating fluid pathway c632 occurring third, such as accordingto the third circumferential series.

In some embodiments, a heat transfer region c622 may include a pistonbody c700 and/or a regenerator body c800, and/or a plurality ofworking-fluid pathways c110 fluidly communicating between the pistonbody c700 and/or the regenerator body c800. When a closed-cycle enginec002 includes a plurality of piston bodies, the piston assemblies mayhave a staggered or offset stroke cycle, such that a first piston and asecond piston may be located at different points in respective strokecycles upon least one point of the stroke cycle. For example, the firstpiston may be at a top point of the stroke cycle and the second pistonmay be at a bottom point of the stroke cycle. As another example, thefirst piston may be at a midpoint of the stroke cycle and the secondpiston may be at the top point or the bottom point of the stroke cycle.In some embodiments, engine-working fluid flowing from a piston bodyc700 (e.g., from a piston chamber c112) to a regenerator body c800 mayexhibit a temperature that differs from engine-working fluid flowing inthe opposite direction, from the regenerator body c800 to the pistonbody c700 (e.g., to the piston chamber c112).

The engine-working fluid flowing through the working-fluid pathways c110may exhibit a temperature that depends at least in part on whether theengine-working fluid is flowing towards the regenerator body c800 (e.g.,from the piston body c700) or towards the piston body c700 (e.g., fromthe regenerator body c800). For example, the temperature of theengine-working fluid may exhibit a first temperature when flowingtowards the regenerator body c800 (e.g., from the piston body c700) anda second temperature when flowing towards the piston body c700 (e.g.,from the regenerator body c800). In some embodiments the firsttemperature may be greater than the second temperature.

In some embodiments, the heating fluid such as combustion gas and theengine-working fluid may exhibit a temperature gradient that depends atleast in part on whether the engine-working fluid is flowing towards theregenerator body c800 (e.g., from the piston body c700) or towards thepiston body c700 (e.g., from the regenerator body c800). For example, afirst temperature gradient may correspond to engine-working fluidflowing towards the regenerator body c800 (e.g., from the piston bodyc700) and a second temperature gradient may correspond to engine-workingfluid flowing towards the piston body c700 (e.g., from the regeneratorbody c800). In some embodiments the first temperature gradient may besmaller than the second temperature gradient. In some embodiments thesecond temperature gradient may be greater than the first temperaturegradient. For example, the first temperature gradient may be smallerthan the second temperature gradient at least in part because of thetemperature of the engine-working fluid flowing towards the regeneratorbody c800 (e.g., from the piston body c700) being greater than thetemperature of engine-working fluid flowing towards the piston body c700(e.g., from the regenerator body c800).

In some embodiments, the rate and/or quantity of heat transfer from theheating fluid to the engine-working fluid may depend on whether theengine-working fluid is flowing towards the regenerator body c800 (e.g.,from the piston body c700) or towards the piston body c700 (e.g., fromthe regenerator body c800). For example, a first rate and/or quantity ofheat transfer from the heating fluid to the engine-working fluid maycorrespond to engine-working fluid flowing towards the regenerator bodyc800 (e.g., from the piston body c700) and a second rate and/or quantityof heat transfer from the heating fluid to the engine-working fluid maycorrespond to engine-working fluid flowing towards the piston body c700(e.g., from the regenerator body c800). In some embodiments the firstrate and/or quantity of heat transfer may be smaller than the secondrate and/or quantity of heat transfer. In other words, the second rateand/or quantity of heat transfer may be greater than the first rateand/or quantity of heat transfer. For example, the first rate and/orquantity of heat transfer may be smaller than the second rate and/orquantity of heat transfer at least in part because of the firsttemperature gradient corresponding to engine-working fluid flowingtowards the regenerator body c800 (e.g., from the piston body c700)being smaller than the second temperature gradient corresponding toengine-working fluid flowing towards the piston body c700 (e.g., fromthe regenerator body c800).

In some embodiments, the heating efficiency of the heater body c100 maybe enhanced at least in part by the second rate and/or quantity of heattransfer corresponding to engine-working fluid flowing towards thepiston body c700 (e.g., from the regenerator body c800) being greaterthan the first rate and/or quantity of heat transfer corresponding toengine-working fluid flowing towards the regenerator body c800 (e.g.,from the piston body c700). For example, in this way, a relativelylarger proportion of the heat input by the heater body c100 may beapplied to the engine-working fluid as the engine-working fluid flowstowards the piston body c700 and thereby drives the piston downward,performing the downstroke portion of a stroke cycle. The heat input tothe engine-working fluid during the downstroke may contribute to thedownstroke (e.g., directly) by further heating and thereby furtherexpanding the engine-working fluid. During the upstroke portion of thestroke cycle, a relatively smaller proportion of the heat input by theheater body c100 may be applied to the engine-working fluid, which mayreduce or mitigate a potential for heat input to the engine-workingfluid to counteract the upstroke by further heating and therebyexpanding the engine-working fluid, providing an additional oralternative efficiency enhancement. With a relatively smaller proportionof the heat input by the heater body c100 applied to the engine-workingfluid during the upstroke, a smaller portion of the heat input may betransferred to the regenerator body c800. While the regenerator bodyc800 may be configured to retain heat, at least some heat transferringto the regenerator body c800 may be lost. By transferring a largerproportion of the heat input of the heater body c100 to theengine-working fluid when flowing towards the piston body c700 (e.g.,from the regenerator body c800), less heat energy may be lost to theregenerator body c800, thereby providing yet another additional oralternative efficiency enhancement.

In some embodiments, at least a portion of the heater body c100 (e.g.,the hot-side heat exchanger body c600 and/or the working-fluid bodyc108) may be configured such that the temperature gradient between thetemperature gradient between the heating fluid and the engine-workingfluid is relatively small when the engine-working fluid is flowingtowards the regenerator body c800. For example, the temperature gradientbetween the heating fluid and the engine-working fluid may be minimalwhen the engine-working fluid is flowing towards the regenerator bodyc800. With a relatively small and/or minimal temperature gradient, therate and/or quantity of heat transfer to the engine-working fluid whenflowing towards the regenerator body c800 may be minimal or nominal.Additionally, or in the alternative, at least a portion of the heaterbody c100 (e.g., the hot-side heat exchanger body c600 and/or theworking-fluid body c108) may be configured such that the temperaturegradient between the temperature gradient between the heating fluid andthe engine-working fluid is relatively large when the engine-workingfluid is flowing towards the piston body c700. For example, thetemperature gradient between the heating fluid and the engine-workingfluid may be maximal when the engine-working fluid is flowing towardsthe piston body c700. With a relatively large and/or maximal temperaturegradient, the rate and/or quantity of heat transfer to theengine-working fluid when flowing towards the regenerator body c800 maybe maximized.

In some embodiments, the rate and/or quantity of heat transferred fromthe heating fluid to the engine-working fluid may exhibit a ratio ofheat transfer when flowing towards the piston body c700 to heat transferwhen flowing towards the regenerator body c800 of from about 1:1 toabout 100:1, such as from about 2:1 to about 100:1, such as from about2:1 to about 10:1, such as from about 10:1 to about 20:1, such as fromabout 20:1 to about 50:1, or such as from about 50:1 to about 100:1. Theratio may be at least 1:1, such as at least 2:1, such as at least 10:1,such as at least 20:1, such as at least 50:1, or such as at least 90:1.The ratio may be less than 100:1, such as less than 90:1, such as lessthan 50:1, such as less than 20:1, such as less than 10:1, or such asless than 2:1.

As the heating fluid flows through the plurality of heating fluidpathways c602, heat may preferentially transfer to heat transfer regionsc612 where the temperature gradient is larger or largest, therebypreferentially providing heat to the heat transfer regions where heat isneeded more or most, for example, in favor of other heat transferregions c612 with a lower or lowest temperature gradient. In someembodiments, heat may preferentially transfer to heat transfer regions(e.g., to engine-working fluid flowing through working-fluid pathwaysc110 therein) corresponding to a piston during a downstroke portion ofthe stroke cycle relative to heat transfer regions corresponding to apiston during an upstroke portion of the stoke cycle. Such preferentialheat transfer may be accomplished at least in part by providing arelatively greater temperature gradient during the downstroke portion ofthe stroke cycle as described. With the plurality of heating fluidpathways c602 defining a spiral pathway, as shown for example in FIGS.4.4.1A through 4.4.2B, the plurality of heating fluid pathways c602 mayencounter all or a portion of the heat transfer regions c612, therebyallowing for preferential heat transfer to the heat transfer regionsc612 where the temperature gradient is larger or largest.

In some embodiments, a hot-side heat exchanger body c600 may include acombustion chamber c102 disposed annularly about an axis c204. Ahot-side heat exchanger body c600 may additionally include aconditioning conduit c122 circumferentially surrounding the combustionchamber c102. The conditioning conduit c122 may fluidly communicate withthe combustion chamber c102 at a distal portion c202 of the combustionchamber c102.

In some embodiments, as shown for example in FIGS. 4.4.2A and 4.4.2B,and 4.4.3A and 4.4.3B, a hot-side heat exchanger body c600 may include aplurality of combustion fins c450 circumferentially spaced about theperimeter of the combustion chamber c102 (and/or disposed radially aboutthe perimeter of the combustion chamber c102). The plurality ofcombustion fins c450 may occupy a radially or concentrically inwardportion of the hot-side heat exchanger body c600. In some embodiments, aportion of the hot-side heat exchanger body c600 may define a secondcombustion chamber c448. The second combustion chamber c448 may includea plurality of combustion fins c450 circumferentially spaced about theperimeter of the combustion chamber c102 (and/or disposed radially aboutthe perimeter of the combustion chamber c102). The plurality ofcombustion fins c450 may define at least a portion of the plurality ofheating fluid pathways c602. Additionally, or in the alternative, theplurality of combustion fins c450 may define a plurality ofcombustion-gas pathways c422 fluidly communicating upstream with thecombustion chamber c102 and downstream with a corresponding plurality ofheating fluid pathways c602. Such combustion-gas pathways c422 mayconcurrently define at least a portion of the second combustion chamberc448 and at least a portion of the plurality of heating fluid pathwaysc602. The second combustion chamber c448 may allow combustion to takeplace at an air-to-fuel ratio closer to the stoichiometric air-to-fuelratio.

The plurality of combustion fins c450 may be monolithically integratedwith corresponding ones of a plurality of heating walls c616 thatrespectively define the plurality of heating fluid pathways c602.Additionally, or in the alternative, the combustion fins c450 and theheating walls c616 may be spaced apart from one another, such as with agap or pathway between an upstream end of the heating walls c602 and adownstream end of the combustion fins c450. The portion of a heatingfluid pathways c602 defined by the combustion fins c450 may be referredto as combustion-gas pathways c422. The combustion-gas pathways c422 mayat least partially occupy the region of the hot-side heat exchanger c106where combustion is configured to occur. Combustion may occur in thecombustion-gas pathways c42 at least in part by the combustion fins c450being heated to a sufficiently high temperature during operation toprevent flame quenching.

The plurality of heating fluid pathways c602 may fluidly communicatewith the outlet plenum c608 at a corresponding plurality ofcircumferential locations about the hot-side heat exchanger body c600.By way of example, a first heating fluid pathway c618 may fluidlycommunicate with an outlet plenum c608 at a first circumferentiallocation c634 about a circumferential axis of the hot-side heatexchanger c106. The first circumferential location c634 may be fromabout 0 to 30 degrees about the circumferential axis, such as from about0 to 15 degrees on the circumferential axis. A second heating fluidpathway c628 may fluidly communicate with an outlet plenum c608 at asecond circumferential location c636 about the circumferential axis. Thesecond circumferential location c636 may be from about 90 to 120 degreesabout the circumferential axis, such as from about 90 to 105 degreesabout the circumferential axis. A third heating fluid pathway c630 mayfluidly communicate with an outlet plenum c608 at a thirdcircumferential location c638 about the circumferential axis. The thirdcircumferential location c638 may be from about 180 to 210 degrees aboutthe circumferential axis, such as from about 180 to 195 degrees aboutthe circumferential axis c205. A fourth heating fluid pathway c632 mayfluidly communicate with an outlet plenum c608 at a fourthcircumferential location c640 about the circumferential axis c205. Thefourth circumferential location c640 may be from about 270 to 300degrees about the circumferential axis c205, such as from about 270 to285 degrees about the circumferential axis c205.

A hot-side heat exchanger body c600 and/or a working-fluid body c108 maydefine any number of heat transfer regions c612. For example, heatexchanger body c600 and/or a working-fluid body c108 may define from 1to 10 heat transfer regions c612, such as from 2 to 8 heat transferregions c612, such as from 3 to 5 heat transfer regions. A plurality ofheat transfer regions c612 may be circumferentially spaced about thehot-side heat exchanger body, such as at respective circumferentialregions about the circumferential axis c205. As shown, four heattransfer regions c612 may be circumferentially spaced about the hot-sideheat exchanger body c600. By way of example, a first heat transferregion c620 may be disposed about a first circumferential segment orsector about the circumferential axis c205 of the hot-side heatexchanger c106. The first circumferential segment or sector may be fromabout 270 to about 360 degrees about the circumferential axis c205. Asecond heat transfer region c622 may be disposed about a secondcircumferential segment or sector about the circumferential axis c205.The second circumferential segment or sector may be from about 180 toabout 270 degrees about the circumferential axis c205. A third heattransfer region c624 may be disposed about a third circumferentialsegment or sector about the circumferential axis c205. The third heattransfer region c624 may be from about 90 to about 180 degrees about thecircumferential axis c205. A fourth heat transfer region c626 may bedisposed about a fourth circumferential segment or sector about thecircumferential axis c205. The fourth circumferential segment or sectormay be from about 0 to about 90 degrees about the circumferential axisc205.

A hot-side heat exchanger body c600 and/or a hot-side heat exchangerc106 may include any number of heating fluid pathways c602. For example,a hot-side heat exchanger body c600 and/or a hot-side heat exchangerc106 may include from 1 to 96 heating fluid pathways c602, such as from1 to 48 heating fluid pathways c602, such as from 4 to 32 heating fluidpathways c602, such as from 8 to 24 heating fluid pathways c602, such asfrom 12 to 20 heating fluid pathways c602, such as from 4 to 16 heatingfluid pathways c602, such as from 4 to 8 heating fluid pathways c602,such as at least 4, at least 8, at least 16, or at least 32 heatingfluid pathways c602.

In some embodiments, at least some of the plurality of heating fluidpathways c602 may have a substantially uniform cross-sectional widthand/or a substantially uniform cross-sectional area. The substantiallyuniform cross-sectional width and/or a substantially uniformcross-sectional area of a heating fluid pathway c602 may be presentalong at least a portion of a length of the heating fluid pathway c602.

At least some of the heating fluid pathways c602 may define a spiralpathway spiraling annularly or semi-annularly around a longitudinal axisA 214. A spiral pathway may follow a spiral arc having any desiredcurvature. The spiral arc may continue along all or a portion of thespiral pathway defined by the heating fluid pathway c602. By way ofexample, a spiral and/or a spiral arc, such as in a spiral pathway, maycorrespond to at least a portion of an Archimedean spiral, a Cornuspiral, a Fermat's spiral, a hyperbolic spiral, a logarithmic spiral, aFibonacchi spiral, an involute, or a squircular spiral, as well ascombinations of these. As shown, in some embodiments the plurality ofheating fluid pathways c602 may define a squircular spiral. At least aportion of a squircular spiral may include an arc corresponding to asquircle. The plurality of heating fluid pathways c602 may have an arclength of from 180 degrees to 1260 degrees, such as from 180 degrees to450 degrees, such as from 315 degrees to 765 degrees, such as from 675degrees to 1260 degrees.

In some embodiments, the plurality of heating fluid pathways c602 mayinclude radially or concentrically adjacent pathways. Additionally, orin the alternative, the plurality of heating fluid pathways c602 mayinclude one or more inverse pairs. For example, an inverse pair mayinclude a pair of heating fluid pathways c602 fluidly communicating withthe inlet plenum c604 (e.g., the combustion chamber c102) at oppositesides thereof. Additionally, or in the alternative, an inverse pair mayinclude a pair of heating fluid pathways c602 fluidly communicating withthe outlet plenum c608 (e.g., the recirculation annulus c208) atopposite sides thereof. By way of example, a first heating fluid pathwayc618 and a third heating fluid pathway c630 may define an inverse pair.As another example, a second heating fluid pathway c628 and a fourthheating fluid pathway c632 may define an inverse pair. The inverse pairmay follow a spiral arc having any desired curvature, such as a spiralarc inverse pair. For example, the heating fluid pathways c602 maydefine a plurality of spiral arc inverse pairs. In some embodiments, aninverse pair may include a parabolic spiral.

Now referring to FIGS. 4.4.3A and 4.4.3B, further exemplary embodimentsof a hot-side heat exchanger body c600 will be described. As shown, insome embodiments, a hot-side heat exchanger body c600 may have aplurality of heating walls c616 and/or combustion fins c450 thatrespectively include a plurality of conduction breaks c605. Theconduction breaks c605 may be disposed radially or concentricallyoutward relative to the plurality of combustion fins c450, and/orradially or concentrically inward relative to the plurality of heatingwalls c616. The conduction breaks c605 may at least partially inhibitheat conduction from the plurality of combustion fins c450 to theplurality of heating walls c616. The conduction breaks c605 may impart adecrease in thermal conductivity relative to the thermal conductivity ofthe plurality of heating walls c616 and/or the plurality of combustionfins c450. The plurality of heating walls c616 may be configured anarranged in a spiral array or spiral arc, such as an annular orsemiannular spiral array or spiral arc. Additionally, or in thealternative, the plurality of combustion fins c450 may be configured anarranged in a spiral array or spiral arc, such as an annular orsemiannular spiral array or spiral arc. A combustion fins c450 and acorresponding heating wall c616 may follow a common trajectory.Additionally, or in the alternative, one or more combustion fins c450may be staggered or offset from one or more heating walls c616. Thecondition breaks c605 may be configured to reduce heat conduction alongthe plurality of heating walls c616, such as along a radial axis or acircumferential axis. For example, the conduction breaks c450 may reduceheat conduction from a downstream portion of the combustion fins c450 toan upstream portion of the heating walls c616, and/or from an upstreamportion of the plurality of heating walls c616 to a downstream portionof the plurality of heating walls c616. During operation, the combustionfins c450 may operate at a relatively higher temperature at least inpart because of the reduced heat conduction attributable to theconduction breaks.

In some embodiments, a portion of the heating wall c616 upstream from aconduction break c605 may define a combustion fin c450. Additionally, orin the alternative, at least a portion of the heating wall c616downstream from a conduction break c605 may define a heat transfer finc607. The plurality of heating walls c616 may be formed of one or morematerials, and/or may exhibit one or more material properties and/orstructures. For example, the heat transfer fins c607 and the combustionfins c450 may differ from one another in respect of materialcomposition, material properties, and/or material structure. In someembodiments, the heat transfer fins c607 may exhibit a greater thermalconductivity relative to the combustion fins c450. Additionally, or inthe alternative, the combustion fins c450 may exhibit a greater heatcapacity relative to the heat transfer fins c607. A desired thermalconductivity and/or heat capacity may be imparted to the combustion finsc450 and/or the heat transfer fins c607 at least in part by augmentingthe material properties and/or structure during additive manufacturing.For example, the density and/or porosity may be augmented by modifyingadditive manufacturing parameters to impart desired thermodynamicproperties, such as heat capacity properties and/or thermal conductivityproperties. Density and/or porosity may be augmented by modifying thedegree of consolidation of powder material, and/or by providing regionsof unsintered or partially sintered regions of powder material.Additionally, or in the alternative, material structure may be augmentedto impart desired thermodynamic properties. For example, a latticestructure, a porous medium, a cellular structure, or the like may beprovided to impart desired heat capacity properties and/or thermalconductivity properties to the combustion fins c450 and/or the heattransfer fins c607.

The plurality of condition breaks c605 may be disposed circumferentiallyadjacent to one another at the respective ones of the plurality ofheating walls c616. The location of the conduction breaks c605 at therespective heating walls c616 may define a circumferential array ofconduction breaks c605. A plurality of combustion fins c450 may occupy aradially or concentrically inward position of the hot-side heatexchanger body c600 relative to the circumferential array of conductionbreaks c605. At least a portion of the plurality of heating walls c616may define a corresponding plurality of heat transfer fins c607. Theheat transfer fins c616 may occupy a radially or concentrically outwardposition of the hot-side heat exchanger body c600 relative to thecircumferential array of conduction breaks c605. For example, theradially or concentrically outward portion of the heating walls c616 maydefine the heat transfer fins c607.

The plurality of combustion fins c450 may define a correspondingplurality of combustion-gas pathways c422. The plurality of combustionfins c450 and/or the plurality of combustion-gas pathways c422 may beconfigured an arranged in a spiral array, such as a semiannular spiralarray. The plurality of combustion fins c450 may spiral concentricallyoutward from a combustion chamber outlet c412 towards the correspondingconduction break c605. The plurality of combustion fins c450 may bearranged in an array of annular or semiannular substantially concentricspirals and/or substantially concentric spiral arcs relative to thelongitudinal axis c204. The circumferential array of conduction breaksc605 may define a radially or concentrically outward perimeter of theplurality of combustion fins c450.

The plurality of heat transfer fins c607 may define a correspondingplurality of heating fluid pathways c602. The plurality of heat transferfins c607 and/or the plurality of heating fluid pathways c602 may beconfigured an arranged in a spiral array, such as an annular orsemiannular spiral array. The plurality of heat transfer fins c607 mayspiral concentrically outward from the corresponding conduction breaks,transecting respective ones of the plurality of heat transfer regionsc612. The circumferential array of conduction breaks c605 may define aradially or concentrically inward perimeter of the plurality of heatingwalls c616. Additionally, or alternatively, the circumferential array ofconduction breaks c605 may define a radially or concentrically inwardperimeter of the plurality of heat transfer regions c612. For example,the plurality of working-fluid bodies c108 and/or the plurality ofworking-fluid pathways c110 may occupy a region of the hot-side heatexchanger body c600 disposed radially or concentrically outward from thecircumferential array of conduction breaks c605. Additionally, or in thealternative, the portion of the heat transfer fins c607 and/or theheating walls c616 that include working-fluid pathways c110monolithically defined therein may occupy a region of the hot-side heatexchanger body c600 disposed radially or concentrically outward from thecircumferential array of conduction breaks c605.

The plurality of heat transfer regions c612 may respectively include anarray of working-fluid pathways c110, such as a plurality of arrays ofworking fluid pathways c110. The array of working fluid pathways c110may be monolithically defined within respective ones of the plurality ofheating walls c616 (e.g., within respective ones of the plurality ofheat transfer fins c607). The circumferential array of conduction breaksc605 may define a radially or concentrically inward perimeter of theplurality of working-fluid pathways c110. Respective ones of theplurality of arrays of working-fluid pathways c110 may be disposedcircumferentially adjacent to one another about the hot-side heatexchanger body c600. Respective ones of the plurality of arrays ofworking-fluid pathways c110 may define at least a portion of aworking-fluid body c108. A plurality of working-fluid bodies c108 may bedisposed circumferentially adjacent to one another about the hot-sideheat exchanger body c600. The circumferential array of conduction breaksc605 may define a radially or concentrically inward perimeter of theplurality of working-fluid bodies c108.

In some embodiments, at least a portion of fuel combustion may takeplace within the plurality of combustion-gas pathways c422. Combustionthat takes place within the combustion-gas pathways c422 may beattributable at least in part to the reduced heat conduction along theheating walls c616 provided by the conduction breaks c605. In someembodiments, the conduction breaks c605 may prevent or reduce apossibility that combustion may quenching prematurely. During operation,the combustion fins c450 may reach a sufficiently high temperature forstable combustion to take place within the plurality of combustion-gaspathways c422 without being prematurely quenched, such as by conductiveheat transfer along the heating walls c616 and into the working-fluidbodies c108. The reduction in heat conduction provided by the conductionbreaks c605 may reduce the potential that heat transfer to the workingfluid-pathways c610 may decrease the temperature of the heating wallsc616 to a level that prematurely quenches combustion.

The conduction breaks c605 may allow the combustion fins to remain at asufficiently high temperature to allow fuel combustion to approachcomplete combustion within the plurality of combustion-gas pathwaysc422. The circumferential array of conduction breaks c605 may be locatedat a distance along the combustion-gas pathways c422 selected to allowsufficient time for complete combustion upon the combustion gas havingencountered the conduction breaks c605. In this way, the conductionbreaks may provide for reduced emissions attributable to completecombustion and a corresponding reduction of unburnt combustion productsin exhaust gas. The plurality of heat transfer regions c612 and/or thearrays of working-fluid pathways c110 may be located substantiallyimmediately downstream from the circumferential array of conductionbreaks c605, thereby allowing the hot combustion gas to begin heatingthe working fluid in the working-fluid pathways substantiallyimmediately upon complete combustion.

As used herein, the term “complete combustion” refers to a state of fuelcombustion that yields carbon dioxide and water as the combustionproducts with an absence of hydrocarbons. Complete combustion may yieldcarbon monoxide as a combustion product on the order ofparts-per-million, such as single-digit parts-per-million (ppm). Forexample, with complete combustion, carbon monoxide may be present as acombustion product in an amount of less than 10 ppm, such as less than 5ppm, or such as less than 1 ppm. In some embodiments, completecombustion may be qualitatively characterized by a blue flame, whereasincomplete combustion may be qualitatively characterized by an orangeflame.

In some embodiments, a heater body c100 may be configured to burn fuelin a lean combustion environment. As mentioned, a lean combustionenvironment may be characterized by an equivalence ratio (i.e., theratio of the actual fuel-to-air ratio to the stoichiometric fuel-to-airratio), such as an equivalence ratio of from about 0.5 to about 1.0,such as from about 0.6 to about 0.9, or from about 0.7 to about 0.8. Alean combustion environment may generate a relatively longer flamelength, which may otherwise point to a relatively larger combustion zoneas an approach for reducing the potential for premature quenching and/orto allow for complete combustion.

In some embodiments, a heater body c100 configured to allow combustionto take place within the combustion-gas pathways c422 not only allowsfor complete combustion; but additionally, or in the alternative, aheater body c100 configured to allow fuel combustion within theplurality of combustion-gas pathways c422 may allow a heater body c100to be operated at a higher equivalence ratio, thereby improving fuelefficiency and/or heating efficiency, while reducing emissions.Additionally, or in the alternative, the heater body c100 may beconfigured with a relatively smaller combustion chamber c102, therebyreducing material costs and weight.

In some embodiments, a combustion zone may occupy a position thatincludes the combustion-gas pathways c422. For example, thecombustion-gas pathways c422 may define at least a portion of a secondcombustion zone c407 as described herein. The circumferential array ofconduction breaks c605 may define a radially or concentrically outwardperimeter of the second combustion zone c407. In some embodiments, thearray of conduction breaks c605 may define an array of burner gaps c421.Such burner gaps may be configured as described herein. Additionally, orin the alternative, a hot-side heat exchanger body c600 may include bothan array of conduction breaks c605 and an array of burner gaps c421.

The combustion fins c450 may be spatially separated from the heatingwalls c616 (e.g., the heat transfer fins c607), such that a conductionbreak c605 may include a physical gap or space defined by the spatialseparation between a combustion fin c450 and heating wall c616 (e.g., aheat transfer fin c607). Additionally, or in the alternative, aconduction break c605 may include a change in a material property, achange in material composition, and/or a change in structure relative tothe combustion fin c450 and/or the heat transfer fin c607 that providesa reduction in heat conduction relative to the combustion fin c450and/or the heat transfer fin c607. For example, a conduction break c605may include a structure such as a mesh, a three-dimensional lattice, aporous medium, or unsintered or partially sintered powder material, aswell as combinations of these.

As shown in FIG. 4.4.3B, The plurality of heating walls c616 and/orcombustion fins c450 may have a plurality of openings c451 (e.g.,pore-like openings) that fluidly communicate with the plurality ofcombustion-gas pathways c422 of the hot-side heat exchanger c106 anddefine the hot-zone fuel injectors c413. In some embodiments, at least aportion of the hot-zone fuel pathways c415 may define a vaporizationheat exchanger c417 that provides a heat transfer relationship between acombustion flame c426 and fuel within the hot-zone fuel pathways c415,and or between hot combustion gas c426 fuel within the hot-zone fuelpathways c415. The vaporization heat exchanger c417 may be effective tovaporize fuel (e.g., liquid fuel), such as when the fuel is within thehot-zone fuel pathways c415 and/or the hot-zone fuel injectors c413, oras the fuel is discharged from the openings (e.g., the pore-likeopenings) of the hot-zone fuel injectors c413.

Now referring to FIG. 4.4.4, exemplary methods of heating a plurality ofheat transfer regions will be described. The exemplary methods ofheating a plurality of heat transfer regions may include, for example,methods of heating one or more working-fluid bodies c108. For example,exemplary methods may be performed in connection with operation of ahot-side heat exchanger body c600, a working-fluid body c108, a heaterbody c100, and/or a closed-cycle engine c002 as described herein. Asshown in FIG. 4.4.4, an exemplary method c650 may include, at blockc652, flowing a first heat transfer fluid through a plurality of heatingfluid pathways c602 fluidly communicating with an inlet plenum c604.Respective ones of the plurality of heating fluid pathways c602 maydefine a spiral pathway. The exemplary method c650 may include, at blockc654, transferring heat from the first heat transfer fluid to aplurality of heat transfer regions c612. Respective ones of theplurality of heat transfer regions c612 may have a heat transferrelationship with a corresponding semiannular portion of the pluralityof heating fluid pathways c602.

In some embodiments, transferring heat from the first heat transferfluid to the plurality of heat transfer regions, at block 654, mayinclude transferring heat from the plurality of heating fluid pathwaysc602 to at least some of the plurality of heat transfer regions c612 incircumferential series. The circumferential series of a respective oneof the plurality of heating fluid pathways c612 may have a sequencedepending at least in part on a circumferential location of an inletc606 to the respective one of the plurality of heating fluid pathwaysc602.

Now referring to FIGS. 4.5.2 and 4.5.3, exemplary working-fluid bodiesc108 will be described. The presently disclosed working-fluid bodiesc108 may define part of a heater body c100 and/or a closed-cycle enginec002. For example, a working-fluid body c108 may define at least aportion of a monolithic body or a monolithic body-segment. Suchmonolithic body or monolithic body-segment may define at least a portionof the heater body c100 and/or the closed-cycle engine c002.Additionally, or in the alternative, the presently disclosedworking-fluid bodies c108 may be provided as a separate component,whether for use in connection with a heater body c100, a closed-cycleengine c002, or any other setting whether related or unrelated to aheater body c100 or a closed-cycle engine c002. At least a portion ofthe working-fluid bodies c108 may define a one or more piston bodiesc700, one or more regenerator bodies c800, and/or one or moreworking-fluid pathway c110. It will be appreciated that a heater bodyc100 may include any desired number of working-fluid bodies c108,including any desired number of piston bodies c700, regenerator bodiesc800, and/or working-fluid pathways c110. For example, a heater bodyc100 may include one or more working-fluid bodies c108, and/or aworking-fluid body c108 may include one or more piston bodies c700,regenerator bodies c800, and/or working-fluid pathways c110.

A working-fluid body c108 may define a first portion of a monolithicbody and the piston body c700 may defines a second portion of themonolithic body. Alternatively, the piston body c700 may define amonolithic body-segment operably coupled or operably couplable to theworking-fluid body c108. Additionally, or in the alternative, aregenerator body c800 may a second portion of the monolithic body, orthe regenerator body c800 may define a second monolithic body-segmentoperably coupled or operably couplable to the piston body 700 and/or theworking-fluid body c108.

As shown, an exemplary working-fluid body c108 may include a pluralityof heat transfer regions c612. Respective ones of the plurality of heattransfer regions may include a plurality of working-fluid pathways c110fluidly communicating between a heat input region and a heat extractionregion. The heat input region may include a piston body c700 and theheat extraction region may include a regenerator body c800.

At least some of the plurality of working-fluid pathways c110 may beradially or concentrically adjacent and/or axially adjacent to oneanother. In some embodiments, a heating fluid pathway c602 may bedisposed between radially or concentrically adjacent and/or axiallyadjacent working-fluid pathways c110. Additionally, or in thealternative, at least some of the working-fluid pathways c110 may besemiannular to one another. For example, a working-fluid body c108 mayinclude a plurality of radially or concentrically adjacent semiannularspiral pathways and/or a plurality of axially adjacent semiannularspiral pathways.

The plurality of working-fluid pathways c110 may be disposed axiallyadjacent to corresponding respective ones of the plurality of heatingfluid pathways c602, such as radially or concentrically adjacent spiralheating fluid pathways c602. Respective ones of the plurality ofworking-fluid pathways c110 may have a thermally conductive relationshipwith corresponding respective ones of the plurality of heating fluidpathways c602.

An exemplary working-fluid body c108 may include a first heat transferregion c620, a second heat transfer region c622, a third heat transferregion c624, and/or a fourth heat transfer region c626. The first heattransfer region c620 may include a first plurality of working-fluidpathways c701. The first plurality of working-fluid pathways c701 mayinclude semiannular radially or concentrically adjacent and/or axiallyadjacent spiral pathways. The second heat transfer region c622 mayinclude a second plurality of working-fluid pathways c702. The secondplurality of working-fluid pathways c702 may include semiannularradially or concentrically adjacent and/or axially adjacent spiralpathways. The third heat transfer region c624 may include a thirdplurality of working-fluid pathways c703. The third plurality ofworking-fluid pathways c703 may include semiannular radially orconcentrically adjacent and/or axially adjacent spiral pathways. Thefourth heat transfer region c626 may include a fourth plurality ofworking-fluid pathways c704. The fourth plurality of working-fluidpathways c704 may include semiannular radially or concentricallyadjacent and/or axially adjacent spiral pathways.

The first heat transfer region c620 may be circumferentially adjacent tothe second heat transfer region c622. The second heat transfer regionc622 may be circumferentially adjacent to the third heat transfer regionc624. The third heat transfer region c624 may be circumferentiallyadjacent to the fourth heat transfer region c626. The fourth heattransfer region c626 may be circumferentially adjacent to the first heattransfer region c620.

The first plurality of working-fluid pathways c701 may becircumferentially adjacent to the second plurality of working-fluidpathways c702. The second plurality of working-fluid pathways c702 maybe circumferentially adjacent to the third plurality of working-fluidpathways c703. The third plurality of working-fluid pathways c703 may becircumferentially adjacent to the fourth plurality of working-fluidpathways c704. The fourth plurality of working-fluid pathways c704 maybe circumferentially adjacent to the first plurality of working-fluidpathways c701.

In some embodiments, respective ones of the plurality of working-fluidpathways c110 may include circumferentially adjacent working-fluidpathways c110. The circumferentially adjacent working-fluid pathways maycircumferentially initiate and/or circumferentially terminate a spiralarray c706 of working-fluid pathways c110. The spiral array c706 maydiverge radially or concentrically outward. The spiral array c706 maytransition from radially or concentrically inward to radially orconcentrically midward and/or from radially or concentrically midward toradially or concentrically outward, as the spiral array c706 passes fromone heat transfer region to the next.

At least some of the working-fluid pathways c110 may define a spiralpathway spiraling annularly or semi-annularly around a longitudinal axisA 214. A spiral pathway may follow a spiral arc having any desiredcurvature. The spiral arc may continue along all or a portion of thespiral pathway defined by the working-fluid pathways c110. By way ofexample, the spiral or spiral arc may correspond to at least a portionof an Archimedean spiral, a Cornu spiral, a Fermat's spiral, ahyperbolic spiral, a logarithmic spiral, a Fibonacchi spiral, aninvolute, or a squircular spiral, as well as combinations of these. Asshown, in some embodiments the plurality of working-fluid pathways c110may define a squircular spiral. At least a portion of a squircularspiral may include an arc corresponding to a squircle. The plurality ofworking-fluid pathways c110 may have an arc length of from 180 degreesto 1260 degrees, such as from 180 degrees to 450 degrees, such as from315 degrees to 765 degrees, such as from 675 degrees to 1260 degrees.

In some embodiments, the plurality of working-fluid pathways c110 mayinclude radially or concentrically adjacent pathways. Additionally, orin the alternative, the plurality of working-fluid pathways c110 mayinclude one or more inverse pairs. For example, an inverse pair mayinclude a pair of working-fluid pathways c110 respectively fluidlycommunicating with a corresponding heat extraction region (e.g., aregenerator body c800) at opposite sides of the working-fluid body c108.Additionally, or in the alternative, an inverse pair may include a pairof working-fluid pathways c110 respectively fluidly communicating with acorresponding heat input region (e.g., a piston body c700) at oppositesides of the working-fluid body c108. The inverse pair may follow aspiral arc having any desired curvature, such as a spiral arc inversepair. For example, the heating fluid pathways c602 may define aplurality of spiral arc inverse pairs. In some embodiments, an inversepair may include a parabolic spiral.

Referring again to FIG. 4.5.2, a working-fluid body c108 may include aplurality of working-fluid pathways c110 interleaved with a plurality ofheating fluid pathways c602 of a hot-side heat exchanger body c600, suchas to provide a thermally conductive relationship therebetween.Respective ones of the plurality of working-fluid pathways c110 may bedisposed alternatingly adjacent to respective ones of the plurality ofheating fluid pathways c602. In some embodiments, a portion of theworking-fluid body c108 defining at least some of the working-fluidpathways c110 may protrude into adjacent respective ones of theplurality of heating fluid pathways c602. Additionally, or in thealternative, at least a portion of the hot-side heat exchanger body c600defining at least some of the heating fluid pathways c602 may protrudeinto adjacent respective ones of the plurality of working-fluid pathwaysc110. For example, a portion of the working-fluid body c108 and/or aportion of the hot-side heat exchanger body c600 defining alternatinglyadjacent working-fluid pathways c110 and heating fluid pathways c602 mayprotrude into such working-fluid pathways c110 and/or heating fluidpathways c602. The protruding portion of the working-fluid body c108and/or hot-side heat exchanger body c600 may protrude in any directiontowards an adjacent working-fluid pathways c110 and/or heating fluidpathways c602. For example, the working-fluid body c108 and/or hot-sideheat exchanger body c600 may protrude radially or concentrically inwardand/or radially or concentrically outward.

The protruding portions of the working-fluid body c108 and/or a portionof the hot-side heat exchanger body c600 may define conduction-enhancingprotuberances c728. The conduction-enhancing protuberances c728 mayenhance conduction between the heating fluid and the engine-workingfluid, for example, by disrupting a boundary layer between the heatingfluid and the heating fluid pathways c602 and/or by a disruptingboundary layer between the engine-working fluid and the working-fluidpathways c110. Respective ones of the plurality of conduction-enhancingprotuberances c728 may be defined at least in part by a portion of theworking-fluid body c108 corresponding to respective ones of a pluralityof working-fluid pathways c110 protruding into adjacent respective onesof a plurality of heating fluid pathways c602. Additionally, or in thealternative, respective ones of the plurality of conduction-enhancingprotuberances c728 may be defined at least in part by a portion of thehot-side heat exchanger body c600 corresponding to respective ones of aplurality of heating fluid pathways c602 protruding into adjacentrespective ones of the plurality of working-fluid pathways c110.

Exemplary conduction-enhancing protuberances may include any one or moreof a combination of protuberant features having a variety of shapes andconfigurations, including nodules, loops, hooks, bumps, burls, clots,lumps, knobs, projections, protrusions, swells, enlargements,outgrowths, accretions, blisters, juts, and the like. Theseconduction-attenuating protuberances c728 occur in an ordered,semi-ordered, random, or semi-random fashion. However, the particularconfiguration, arrangement, or orientation of the conduction-enhancingprotuberances c728 may be selectively controlled or modified byadjusting the configuration or arrangement of at least a portion of theworking-fluid body c108 and/or hot-side heat exchanger body c600, suchas the configuration or arrangement of at least a portion of theworking-fluid pathways c110 and/or heating fluid pathways c602.

Now referring to FIG. 4.5.3, another exemplary cross-sectional view of aworking-fluid body c108 will be described. As shown in FIG. 4.5.3, aplurality of piston bodies c700 and a plurality of regenerator bodiesc800 may be circumferentially spaced about a longitudinal axis c204 ofthe working-fluid body c108. The plurality of piston bodies c700 andregenerator bodies c800 may be paired with one another, for example,with a plurality of working-fluid pathways c110 fluidly communicationbetween respective piston body c700 and regenerator body c800 pairs. Forexample, a first plurality of working-fluid pathways c701 may fluidlycommunicate between a first piston chamber c112 defined by a firstpiston body c700 and a first regenerator chamber c802 defined by a firstregenerator body c800. A second plurality of working-fluid pathways c702may fluidly communicate between a second piston chamber c112 defined bya second piston body c700 and a second regenerator chamber c802 definedby a second regenerator body c800. A third plurality of working-fluidpathways c703 may fluidly communicate between a third piston chamberc112 defined by a third piston body c700 and a third regenerator chamberc802 defined by a third regenerator body c800. A fourth plurality ofworking-fluid pathways c704 may fluidly communicate between a fourthpiston chamber c112 defined by a fourth piston body c700 and a fourthregenerator chamber c802 defined by a fourth regenerator body c800.

A flow direction of engine-working fluid flowing through a plurality ofworking-fluid pathways c110 may be counter-current or co-currentrelative to a flow direction c732 of heating fluid flowing through theheating fluid pathways c602 adjacent to such working-fluid pathwaysc110. For example, as shown, engine-working fluid flowing from a pistonchamber c112 towards a regenerator chamber c802 may be counter-currentto the flow direction c732 of the heating fluid flowing through adjacentheating fluid pathways c602. Engine-working fluid flowing from aregenerator chamber c802 towards a piston chamber c112 may be co-currentto the flow direction c732 of the heating fluid flowing through adjacentheating fluid pathways c602. Alternatively, in other embodiments,engine-working fluid may be counter-current to the flow direction c732of the heating fluid when flowing from a piston chamber c112 towards aregenerator chamber c802 and co-current when flowing from a regeneratorchamber c802 towards a piston chamber c112.

In a general sense, heat transfer from a hot fluid to a cold fluid maybe greater during counter-current flow relative to co-current flow. Forexample, with co-current flow, the temperature of the cold fluid may bealways less than the temperature of the hot fluid, and as such, heattransfer may be restricted by the discharge temperature of the coldfluid. Conversely, with counter-currently flow, heat transfer is notrestricted by the discharge temperature of the cold fluid, which mayallow for a greater quantity of heat transfer. On the other hand, withco-current flow, the temperature gradient between a hot fluid and a coldfluid may be greater at an initial zone of heat transfer prior toachieving thermal equilibrium, relative to the temperature gradient atan initial zone of heat transfer with counter-current flow. As such,faster heat transfer may be achieved during non-equilibrium conditionsduring co-current flow.

In some embodiments, it may be advantageous for heating fluid to flowco-currently relative to engine-working fluid when the engine-workingfluid flows from the regenerator body c800 to the piston body c700. Forexample, the temperature gradient between the engine-working fluid andthe heating fluid may be greater when the engine-working fluid flowsfrom the regenerator body c800 towards the piston body c700 relative toengine-working fluid flowing in the opposite direction. Such temperaturegradient may be greater, for example, because of heat losses as heattransfers from the engine-working fluid to the regenerator body c800 andback to the engine-working fluid. With a greater temperature gradientexisting when engine-working fluid flows from the regenerator body c800towards the piston body c700, such temperature gradient may facilitate amore rapid heat transfer from the heating fluid to the engine-workingfluid. In particular, such temperature gradient may facilitate a morerapid heat transfer to the engine-working fluid as the engine-workingfluid flows into the piston body c800, thereby further expanding theengine-working fluid and contributing to the downstroke (e.g., directly)of the piston within the piston chamber. Additionally, or in thealternative, with heating fluid flowing counter-current relative toengine-working fluid flowing from the piston body c700 to theregenerator body c800, the rate of heat transfer from the heating fluidto the engine-working fluid may be less than when the engine-workingfluid flows in the opposite direction. As such, relatively less heattransfer may be imparted to the engine-working fluid when flowing intothe regenerator body c800 the engine-working fluid flows from theregenerator body c800, further contributing to efficiency of the heaterbody c100, such as when inputting heat to the closed-cycle engine c002.

Any suitable engine-working fluid may be utilized in accordance with thepresent disclosure. In exemplary embodiments, the engine-working fluidmay include a gas, such as an inert gas. For example, a noble gas, suchas helium may be utilized as an engine-working fluid. Exemplaryengine-working fluids preferably are inert, such that they generally donot participate in chemical reactions such as oxidation within theenvironment of the working-fluid body c108. Exemplary noble gassesinclude monoatomic gases such as helium, neon, argon, krypton, or xenon,as well as combinations of these. In some embodiments, an engine-workingfluid may include air, oxygen, nitrogen, or carbon dioxide, as well ascombinations of these.

Now turning to FIGS. 4.5.5A-4.5.5D, exemplary thermal expansion jointsc135 of a heater body c100 will be described. A heater body c100 mayinclude one or more thermal expansion joints c135 at any one or moredesired locations of the heater body c100. A thermal expansion jointc135 may include an expansion gap c149 configured to allow for thermalexpansion, and/or a difference in thermal expansion, as betweenrespective sides of the thermal expansion joint c135. In someembodiments, a thermal expansion joint c135 may include an expansion gapc149 that provides for a hairpin configuration, as shown, for example,in FIG. 4.5.5B. Such hairpin configuration may provide an extendedthermal conduction pathway as between respective sides of the thermalexpansion joint c135. In some embodiments, the expansion gap c147 mayinclude an insulating material c129, such as a radiative-heat shieldradiative-heat shield c129A (FIGS. 4.1.8A-4.1.8G), to provide animproved view factor and corresponding reduction in radiative heattransfer as between respective sides of the thermal expansion jointc135.

As shown, in some embodiments, a heater body c100 may include one ormore combustor-thermal expansion joints c135A. A combustor-thermalexpansion joint c135A may allow for thermal expansion, and/or adifference in thermal expansion, as between at least a portion of acombustor body c400 and one or more adjacent regions of the heater bodyc100. For example, a combustor-thermal expansion joint c135A may allowfor thermal expansion, and/or a difference in thermal expansion, asbetween a combustor body c400 and a hot-side heat exchanger body c600(such as between a combustion chamber c102 and a hot-side heat exchangerc106). Additionally, or in the alternative, a combustor-thermalexpansion joint c135A may allow for thermal expansion, and/or adifference in thermal expansion, as between a combustor body c400 and aworking-fluid body c108 (such as between a combustion chamber c102 andan array of working-fluid pathways c110).

A combustor-thermal expansion joint c135A may be oriented concentricwith a combustion chamber c102 and/or a longitudinal axis c204 of theheater body c100, as shown, for example in FIGS. 4.5.5A, 4.5.5C and4.5.5D. The combustor-thermal expansion joint c135A maycircumferentially surround at least a portion of the combustor bodyc400. For example, as shown in FIGS. 4.5.5A and 4.5.5B, an expansion gapc149 may be disposed within at least a portion of a hot-side heater bodyc600. Additionally, or in the alternative, the combustor-thermalexpansion joint c135A may be at least partially axially offset from thecombustion chamber c102, as shown. Such axial offset may be configuredto provide an extended thermal conductive pathway as between thecombustor body c400 and the hot-side heat exchanger body c600.

In some embodiments, a heater body c100 may include one or more heattransfer region-thermal expansion joints c135B. A heat transferregion-thermal expansion joint c135B may allow for thermal expansion,and/or a difference in thermal expansion, as between respective heattransfer regions c612 of a heater body c100. For example, a heattransfer region-thermal expansion joint c135B may allow for thermalexpansion, and/or a difference in thermal expansion, as between aworking-fluid body c108 and a regenerator body c800, and/or as between apiston body c700 and a regenerator body c800. As shown in FIGS. 4.5.5Cand 4.5.5D, a heat transfer region-thermal expansion joint c135B may bedisposed between a regenerator body c800 of a first heat transfer regionc620 and a working-fluid body c108 of a second heat transfer region c622(and/or between a regenerator body c800 of a first heat transfer regionc620 and a piston body c700 of a second heat transfer region c622).

Additionally, or in the alternative, a heat transfer region-thermalexpansion joint c135B may be disposed between a heat input region c601of a working-fluid body c108 and a heat extraction region c603 of aworking fluid body c108, such as between a heat input region c601 of afirst heat transfer region c620, and a heat extraction region c603 of asecond heat transfer region c622. Such as heat input region c601includes working-fluid pathways c110 on a side of the working-fluid bodyc108 proximal to the piston body c700, such as including a portion ofthe working-fluid pathways c110 proximal to corresponding piston chamberapertures c111. Such a heat extraction region c603 includesworking-fluid pathways c110 on a side of the working-fluid body proximalto the regenerator body c800, such as including a portion of theworking-fluid pathways c110 proximal to corresponding regeneratorapertures c113.

Now referring to FIG. 4.5.6 exemplary methods of heating anengine-working fluid will be described. The exemplary methods of heatingan engine-working fluid may include, for example, methods of heating oneor more working-fluid bodies c108. For example, exemplary methods may beperformed in connection with operation of a hot-side heat exchanger bodyc600, a working-fluid body c108, a heater body c100, and/or aclosed-cycle engine c002 as described herein. As shown, an exemplarymethod c750 may include, at block c752 flowing an engine-working fluidacross respective ones of a plurality of heat transfer regions c612. Theplurality of heat transfer regions c612 may include a plurality ofworking-fluid pathways c110 fluidly communicating between a heat inputregion such as a piston body c700 and a heat extraction region such as aregenerator c800. The engine-working fluid may flow through theplurality of working-fluid pathways c110, such as alternatingly betweenthe heat input region such as the piston body c700 and the heatextraction region such as the regenerator c800. At block c754, theexemplary method may include transferring heat from a heating source tothe engine-working fluid. The plurality of working-fluid pathways c110may have a heat transfer relationship with the heating source. Theheating source may be a heating fluid, such as combustion gas, which maybe heated using a heater body c100.

An exemplary method c750 may include alternatingly flowing theengine-working fluid from the heat input region to the heat extractionregion, and from the heat extraction region to the heat input region.For example, the method c750 may include alternatingly flowing through afirst plurality of working-fluid pathways c701, a first portion of theengine-working fluid from the heat input region to the heat extractionregion and from the heat extraction region to the heat input region. Insome embodiments, the first portion of the engine-working fluid mayalternatingly flow from the heat input region to a first heat extractionregion and from the first heat extraction region to the heat inputregion. Additionally, or in the alternative, the method c750 may includealternatingly flowing through a second plurality of working-fluidpathways c702, a second portion of the engine-working fluid from theheat input region to the heat extraction region and from the heatextraction region to the heat input region. In some embodiments, thesecond portion of the engine-working fluid may alternatingly flow fromthe heat input region to a second heat extraction region and from thesecond heat extraction region to the heat input region. In anotherembodiment, the first portion of the engine-working fluid mayalternatingly flow between a first heat input region and a first heatextraction region and the second portion of the engine-working fluid mayalternatingly flow between a second heat input region to a second heatextraction region.

Control systems and methods of controlling various systems disclosedherein will now be provided. A control system generates control commandsthat are provided to one or more controllable devices of the system. Thecontrollable devices execute control actions in accordance with thecontrol commands. Accordingly, the desired output of the system can beachieved.

FIG. 5.1.28 provides an example computing system in accordance with anexample embodiment of the present disclosure. The one or morecontrollers, computing devices, or other control devices describedherein can include various components and perform various functions ofthe one or more computing devices of the computing system b2000described below.

As shown in FIG. 5.1.28, the computing system b2000 can include one ormore computing device(s) b2002. The computing device(s) b2002 caninclude one or more processor(s) b2004 and one or more memory device(s)b2006. The one or more processor(s) b2004 can include any suitableprocessing device, such as a microprocessor, microcontroller, integratedcircuit, logic device, and/or other suitable processing device. The oneor more memory device(s) b2006 can include one or more computer-readablemedia, including, but not limited to, non-transitory computer-readablemedia, RAM, ROM, hard drives, flash drives, and/or other memory devices.

The one or more memory device(s) b2006 can store information accessibleby the one or more processor(s) b2004, including computer-readableinstructions b2008 that can be executed by the one or more processor(s)b2004. The instructions b2008 can be any set of instructions that whenexecuted by the one or more processor(s) b2004, cause the one or moreprocessor(s) b2004 to perform operations. In some embodiments, theinstructions b2008 can be executed by the one or more processor(s) b2004to cause the one or more processor(s) b2004 to perform operations, suchas any of the operations and functions for which the computing systemb2000 and/or the computing device(s) b2002 are configured, such as e.g.,operations for controlling certain aspects of power generation systemsand/or controlling one or more closed cycle engines as described herein.For instance, the methods described herein can be implemented in wholeor in part by the computing system b2000. Accordingly, the method can beat least partially a computer-implemented method such that at least someof the steps of the method are performed by one or more computingdevices, such as the exemplary computing device(s) b2002 of thecomputing system b2000. The instructions b2008 can be software writtenin any suitable programming language or can be implemented in hardware.Additionally, and/or alternatively, the instructions b2008 can beexecuted in logically and/or virtually separate threads on processor(s)b2004. The memory device(s) b2006 can further store data b2010 that canbe accessed by the processor(s) b2004. For example, the data b2010 caninclude models, databases, etc.

The computing device(s) b2002 can also include a network interface b2012used to communicate, for example, with the other components of system(e.g., via a network). The network interface b2012 can include anysuitable components for interfacing with one or more network(s),including for example, transmitters, receivers, ports, controllersb1510, antennas, and/or other suitable components. One or morecontrollable devices b1534 and other controllers b1510 can be configuredto receive one or more commands or data from the computing device(s)b2002 or provide one or more commands or data to the computing device(s)b2002.

The technology discussed herein makes reference to computer-basedsystems and actions taken by and information sent to and fromcomputer-based systems. One of ordinary skill in the art will recognizethat the inherent flexibility of computer-based systems allows for agreat variety of possible configurations, combinations, and divisions oftasks and functionality between and among components. For instance,processes discussed herein can be implemented using a single computingdevice or multiple computing devices working in combination. Databases,memory, instructions, and applications can be implemented on a singlesystem or distributed across multiple systems. Distributed componentscan operate sequentially or in parallel.

Although specific features of various embodiments may be shown in somedrawings and not in others, this is for convenience only. In accordancewith the principles of the present disclosure, any feature of a drawingmay be referenced and/or claimed in combination with any feature of anyother drawing.

This written description uses examples to describe the presentlydisclosed subject matter, including the best mode, and also to provideany person skilled in the art to practice the subject matter, includingmaking and using any devices or systems and performing any incorporatedmethods. The patentable scope of the presently disclosed subject matteris defined by the claims, and may include other examples that occur tothose skilled in the art. Such other examples are intended to be withinthe scope of the claims if they include structural elements that do notdiffer from the literal language of the claims, or if they includeequivalent structural elements with insubstantial differences from theliteral languages of the claims.

What is claimed is:
 1. A monolithic heater body, comprising: a combustorbody defining a combustion chamber and a conditioning conduitcircumferentially surrounding the combustion chamber, the conditioningconduit fluidly communicating with the combustion chamber at a distalportion of the combustion chamber; a hot-side heat exchanger bodydefining a hot-side heat exchanger comprising a heating fluid pathwayfluidly communicating with a proximal portion of the combustion chamber;and an eductor body defining an eduction pathway fluidly communicatingwith a downstream portion of the heating fluid pathway and a proximalportion of the conditioning conduit.
 2. The monolithic heater body ofclaim 1, wherein the combustion chamber, the heating fluid pathway, theeduction pathway, and the conditioning conduit together define at leasta portion of a recirculation pathway configured to recirculatecombustion gas through the combustion chamber.
 3. The monolithic heaterbody of claim 1, comprising: a fuel injector body defining a portion ofthe monolithic heater body or operably coupled to the monolithic heaterbody, the fuel injector body comprising a combustor cap defining anozzle port configured to receive a fuel nozzle, the combustor capdisposed axially adjacent to a distal portion of the conditioningconduit.
 4. The monolithic heater body of claim 1, wherein the combustorcap defines at least a portion of a recirculation pathway configured torecirculate combustion gas through the combustion chamber.
 5. Themonolithic heater body of claim 1, wherein the hot-side heat exchangerbody defines a plurality of heating fluid pathways fluidly communicatingwith the proximal portion of the combustion chamber, the plurality ofheating fluid pathways concentrically spiraling about a perimeter of thecombustion chamber.
 6. The monolithic heater body of claim 5, whereinrespective ones of the plurality of heating fluid pathways comprise aspiral pathway.
 7. The monolithic heater body of claim 5, wherein thehot-side heat exchanger body comprises a heat transfer region having aheat transfer relationship with the plurality of heating fluid pathways.8. The monolithic heater body of claim 5, wherein the hot-side heatexchanger body comprises a plurality of heat transfer regionsrespectively disposed about a semiannular portion of the hot-side heatexchanger body, wherein respective ones of the plurality of heattransfer regions have a heat transfer relationship with a correspondingsemiannular portion of the plurality of heating fluid pathways.
 9. Themonolithic heater body of claim 1, comprising: a working-fluid bodydefining a working-fluid pathway fluidly communicating between a heatinput region and a heat extraction region.
 10. The monolithic heaterbody of claim 9, wherein the working-fluid body defines a plurality ofheat transfer regions, respective ones of the plurality of heat transferregions comprising a plurality of working-fluid pathways fluidlycommunicating between a respective one of a plurality of heat inputregions and a respective one of a plurality of heat extraction regions.11. The monolithic heater body of claim 1, wherein the hot-side heatexchanger body comprises a heat transfer region having a heat transferrelationship with a working-fluid body, the working-fluid body defininga working-fluid pathway fluidly communicating between a heat inputregion and a heat extraction region.
 12. The monolithic heater body ofclaim 1, wherein the heat input region comprises a piston body defininga piston chamber and/or wherein the heat extraction region comprises aregenerator body defining a regenerator conduit.
 13. The monolithicheater body of claim 1, wherein the eductor body defines a motivepathway fluidly communicating with the proximal portion of theconditioning conduit.
 14. The monolithic heater body of claim 1,comprising: an intake air body defining an intake air pathway fluidlycommunicating with a motive pathway defined by the eductor body, themotive pathway fluidly communicating with the proximal portion of theconditioning conduit.
 15. The monolithic heater body of claim 1,comprising: a heat recuperator body defining at least a portion of anexhaust pathway and at least a portion of an intake air pathway, theexhaust pathway having a heat transfer relationship with the intake airpathway.
 16. The monolithic heater body of claim 1, wherein themonolithic heater body has an annular configuration.
 17. The monolithicheater body of claim 1, comprising: an inner wall and an outer wall; anda cooling jacket defined between the inner wall and the outer wall;wherein the cooling jacket fluidly communicates with an intake airpathway and a proximal portion of the combustion chamber.
 18. Themonolithic heater body of claim 1, comprising: a thermal expansion jointdisposed annularly or semi-annularly about a longitudinal axis of thecombustion chamber.
 19. The monolithic heater body of claim 1, whereinthe monolithic heater body defines at least a portion of an additivelymanufactured monolithic body or an additively manufactured monolithicbody-segment.
 20. The monolithic heater body of claim 1, wherein themonolithic heater body defines at least a portion of a closed-cycleengine.